|GNU General Public License|
The GNU logo
|Author||Free Software Foundation|
|Copyright||Free Software Foundation, Inc. The Free Software Foundation ( FSF) is a Non-profit corporation founded by Richard Stallman on 4 October 1985 to support the Free software movement Copyright is a legal concept enacted by Governments, giving the creator of an original work of authorship Exclusive rights to control its distribution usually for|
|Published||29 June 2007|
|Linking from code with a different license||No|
The GNU General Public License (GNU GPL or simply GPL) is a widely used free software license, originally written by Richard Stallman for the GNU project. Events 512 - A Solar eclipse is recorded by a monastic chronicler in Ireland. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The Debian Free Software Guidelines ( DFSG) is a set of guidelines that the Debian Project uses to determine whether a software license is a Free software license Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified An open source license is a copyright License for Computer software that makes the source code available under terms that allow for modification and redistribution License compatibility refers to the problem with licenses of software packages which can contain contradictory requirements rendering it impossible to combine Source code A free software licence is a Software licence which grants recipients rights to modify and redistribute the Software which would otherwise be prohibited by Copyright Richard Matthew Stallman (born March 16 1953 often abbreviated " rms " is an American software freedom activist The GNU Project is a Free software, Mass collaboration project announced in 1983 by Richard Stallman. The GPL is the most popular and well-known example of the type of strong copyleft license that requires derived works to be available under the same copyleft. Copyleft is a play on the word Copyright and describes the practice of using copyright law to remove restrictions on distributing copies and modified versions Under this philosophy, the GPL is said to grant the recipients of a computer program the rights of the free software definition and uses copyleft to ensure the freedoms are preserved, even when the work is changed or added to. Computer programs (also software programs, or just programs) are instructions for a Computer. The Free Software Definition, written by Richard Stallman and published by Free Software Foundation (FSF defines Free software - free in the "free This is in distinction to permissive free software licenses, of which the BSD licenses are the standard examples. BSD licenses represent a family of Permissive free software licences.
The GNU Lesser General Public License (LGPL) is a modified, more permissive, version of the GPL, originally intended for some software libraries. The GNU Lesser General Public License (formerly the GNU Library General Public License) or LGPL is a Free software license published by the Free Software In Computer science, a library is a collection of Subroutines used to develop Software. There is also a GNU Free Documentation License, which was originally intended for use with documentation for GNU software, but has also been adopted for other uses, such as the Wikipedia project. The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software ***************************************************************************************** * *
The Affero General Public License (GNU AGPL) is a similar licence with a focus on networking server software. The Affero General Public License, often abbreviated as Affero GPL and AGPL (and sometimes informally called the Affero license) refers to two distinct The GNU AGPL is similar to the GNU General Public License, except that it additionally covers the use of the software over a computer network, requiring that the complete source code be made available to any network user of the AGPLed work, for example a web application. The Free Software Foundation recommends that this license is considered for any software that will commonly be run over the network.
The GPL was written by Richard Stallman in 1989 for use with programs released as part of the GNU project. Richard Matthew Stallman (born March 16 1953 often abbreviated " rms " is an American software freedom activist The GNU Project is a Free software, Mass collaboration project announced in 1983 by Richard Stallman. The original GPL was based on a unification of similar licenses used for early versions of GNU Emacs, the GNU Debugger and the GNU Compiler Collection. Emacs is a class of feature-rich Text editors usually characterized by their extensibility The GNU Debugger, usually called just GDB, is the standard Debugger for the GNU software system The GNU Compiler Collection (usually shortened to GCC) is a set of Compilers produced for various Programming languages by the GNU Project These licenses contained similar provisions to the modern GPL, but were specific to each program, rendering them incompatible, despite being the same license.  Stallman's goal was to produce one license that could be used for any project, thus making it possible for many projects to share code.
An important vote of confidence in the GPL came from Linus Torvalds' adoption of the license for the Linux kernel in 1992, switching from an earlier license that prohibited commercial distribution. Linus Benedict Torvalds ( ˈtuːrvalds born December 28 1969 in Helsinki, Finland) is a Finnish software engineer The Linux kernel has been marked by constant growth throughout its history
As of August 2007, the GPL accounted for nearly 65% of the 43,442 free software projects listed on Freshmeat, and as of January 2006, about 68% of the projects listed on SourceForge.net. Freshmeat is a Website that allows computer users to keep track of the latest software releases and updates as well as write/read reviews and articles send or receive comments Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. SourceForgenet is a Source code repository. It acts as a centralized location for software developers to control and manage open source software development  Similarly, a 2001 survey of Red Hat Linux 7. 1 found that 50% of the source code was licensed under the GPL and a 1997 survey of MetaLab, then the largest free software archive, showed that the GPL accounted for about half of the licenses used. One survey of a large repository of open-source software reported that in July 1997, about half the software packages with explicit license terms used the GPL.  Prominent free software programs licensed under the GPL include the Linux kernel and the GNU Compiler Collection (GCC). Linux is an operating system kernel used by a family of Unix-like Operating systems These are popularly termed Linux operating systems and The GNU Compiler Collection (usually shortened to GCC) is a set of Compilers produced for various Programming languages by the GNU Project Some other free software programs are dual-licensed under multiple licenses, often with one of the licenses being the GPL. Dual-licensing is the practice of distributing Software under two different sets of terms and conditions
Some observers believe that the strong copyleft provided by the GPL was crucial to the success of Linux, giving the programmers who contributed to it the confidence that their work would benefit the whole world and remain free, rather than being exploited by software companies that would not have to give anything back to the community. Copyleft is a play on the word Copyright and describes the practice of using copyright law to remove restrictions on distributing copies and modified versions 
The second version of the license, version 2, was released in 1991. Over the following 15 years, some members of the FOSS (Free and Open Source Software) community came to believe that some software and hardware vendors were finding loopholes in the GPL, allowing GPL-licensed software to be exploited in ways that were contrary to the intentions of the programmers. The free software community is an informal term referring to the users and developers of Free software as well as supporters of the Free software movement. These concerns included tivoization (the inclusion of GPL-licensed software in hardware that will refuse to run modified versions of it); the use of unpublished, modified versions of GPL software behind web interfaces; and patent deals between Microsoft and Linux and Unix distributors that may represent an attempt to use patents as a weapon against competition from Linux. Tivoization is the creation of a system that incorporates Software under the terms of a Copyleft Software license, but uses hardware to prevent users from Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer
Version 3 was developed to attempt to address these concerns. It was officially released on June 29, 2007. Events 512 - A Solar eclipse is recorded by a monastic chronicler in Ireland. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.
Version 1 of the GNU GPL, released in January 1989, prevented what were then the two main ways that software distributors restricted the freedoms that define free software. The first problem was that distributors may publish binary files only – executable, but not readable or modifiable by humans. To prevent this, GPLv1 said that any vendor distributing binaries must also make the human readable source code available under the same licensing terms.
The second problem was the distributors might add additional restrictions, either by adding restrictions to the license, or by combining the software with other software which had other restrictions on its distribution. If this was done, then the union of the two sets of restrictions would apply to the combined work, thus unacceptable restrictions could be added. To prevent this, GPLv1 said that modified versions, as a whole, had to be distributed under the terms in GPLv1. Therefore, software distributed under the terms of GPLv1 could be combined with software under more permissive terms, as this would not change the terms under which the whole could be distributed, but software distributed under GPLv1 could not be combined with software distributed under a more restrictive license, as this would conflict with the requirement that the whole be distributable under the terms of GPLv1.
According to Richard Stallman, the major change in GPLv2 was the "Liberty or Death" clause, as he calls it - Section 7.  This section says that if someone has restrictions imposed that prevent him or her from distributing GPL-covered software in a way that respects other users' freedom (for example, if a legal ruling states that he or she can only distribute the software in binary form), he or she cannot distribute it at all.
By 1990, it was becoming apparent that a less restrictive license would be strategically useful for some software libraries; when version 2 of the GPL (GPLv2) was released in June 1991, therefore, a second license - the Library General Public License (LGPL) was introduced at the same time and numbered with version 2 to show that both were complementary. The version numbers diverged in 1999 when version 2. 1 of the LGPL was released, which renamed it the GNU Lesser General Public License to reflect its place in the GNU philosophy. The GNU Lesser General Public License (formerly the GNU Library General Public License) or LGPL is a Free software license published by the Free Software
In late 2005, the Free Software Foundation (FSF) announced work on version 3 of the GPL (GPLv3). The Free Software Foundation ( FSF) is a Non-profit corporation founded by Richard Stallman on 4 October 1985 to support the Free software movement On January 16, 2006, the first "discussion draft" of GPLv3 was published, and the public consultation began. Events 27 BC - The title Augustus is bestowed upon Gaius Julius Caesar Octavian by the Roman Senate. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. The public consultation was originally planned for nine to fifteen months but finally stretched to eighteen months with four drafts being published. The official GPLv3 was released by FSF on June 29, 2007. Events 512 - A Solar eclipse is recorded by a monastic chronicler in Ireland. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. GPLv3 was written by Richard Stallman, with legal counsel from Eben Moglen and Software Freedom Law Center. Richard Matthew Stallman (born March 16 1953 often abbreviated " rms " is an American software freedom activist Eben Moglen is a professor of law and legal history at Columbia University, and is the founder Director-Counsel and Chairman of Software Freedom Law Center, The Software Freedom Law Center (SFLC is an organization that provides legal representation and related services to protectand advance Free software / Open source 
According to GPLv3 author, Richard Stallman, the most important changes are in relation to software patents, free software license compatibility, the definition of "source code", and hardware restrictions on software modification ("tivoization"). Opposition to Software patents is widespread in the Free software community. A free software licence is a Software licence which grants recipients rights to modify and redistribute the Software which would otherwise be prohibited by Copyright Tivoization is the creation of a system that incorporates Software under the terms of a Copyleft Software license, but uses hardware to prevent users from  Other changes relate to internationalisation, how license violations are handled, and how additional permissions can be granted by the copyright holder.
Other notable changes include allowing authors to add certain additional conditions or requirements to their contributions. One of those new optional requirements, sometimes referred to as the Affero clause, is intended to fulfill a request regarding software as a service; the permitting addition of this requirement makes GPLv3 compatible with the Affero General Public License. Software as a service ( SaaS, typically pronounced 'sass' is a model of Software deployment where an application is hosted as a service provided to customers across The Affero General Public License, often abbreviated as Affero GPL and AGPL (and sometimes informally called the Affero license) refers to two distinct
The public consultation process was coordinated by the Free Software Foundation with assistance from Software Freedom Law Center, Free Software Foundation Europe, and other free software groups. The Software Freedom Law Center (SFLC is an organization that provides legal representation and related services to protectand advance Free software / Open source The Free Software Foundation Europe (FSFE or FSF Europe) was founded in 2001 as an official European sister organization of the U Comments were collected from the public via the gplv3. fsf. org web portal.  That portal runs purpose-written software called stet. stet is a Free software package for gathering comments about a text document via a webpage These comments were passed to four committees comprising approximately 130 people, including supporters and detractors of FSF's goals. Those committees researched the comments submitted by the public and passed their summaries to Stallman for a decision on what the license would do.
The third draft was released on March 28, 2007. Events 37 - Roman Emperor Caligula accepts the titles of the Principate, entitled to him by the Senate. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.  This draft included language intended to prevent patent cross-licenses like the controversial Microsoft-Novell patent agreement and restricts the anti-tivoization clauses to a legal definition of a "User" or "consumer product. Novell Inc ( is a global Software Corporation based in the United States specializing in enterprise operating systems such as SUSE " It also explicitly removed the section on "Geographical Limitations", whose probable removal had been announced at the launch of the public consultation.
The fourth discussion draft, which was the last, was released on May 31, 2007. Events 1279 BC - Rameses II (The Great (19th dynasty becomes pharaoh of Ancient Egypt. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. It introduced Apache Software License compatibility, clarified the role of outside contractors, and made an exception to permit the Microsoft-Novell agreement, saying in section 11 paragraph 6 that
You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license [. . . ]
This aims to make future such deals ineffective. The license is also meant to cause Microsoft to extend the patent licenses it grants to Novell customers for the use of GPLv3 software to all users of that GPLv3 software; this is possible only if Microsoft is legally a "conveyor" of the GPLv3 software. 
Others, notably some high-profile developers of the Linux kernel, commented to the mass media and made public statements about their objections to parts of discussion drafts 1 and 2. Linux is an operating system kernel used by a family of Unix-like Operating systems These are popularly termed Linux operating systems and 
The terms and conditions of the GPL are available to anybody receiving a copy of the work that has a GPL applied to it ("the licensee"). Any licensee who adheres to the terms and conditions is given permission to modify the work, as well as to copy and redistribute the work or any derivative version. The licensee is allowed to charge a fee for this service, or do this free of charge. This latter point distinguishes the GPL from software licenses that prohibit commercial redistribution. The FSF argues that free software should not place restrictions on commercial use, and the GPL explicitly states that GPL works may be sold at any price.
The GPL additionally states that a distributor may not impose "further restrictions on the rights granted by the GPL". This forbids activities such as distributing of the software under a non-disclosure agreement or contract. Distributors under the GPL also grant a license for any of their patents practiced by the software, to practice those patents in GPL software.
Section three of the license requires that programs distributed as pre-compiled binaries are accompanied by a copy of the source code, a written offer to distribute the source code via the same mechanism as the pre-compiled binary or the written offer to obtain the source code that you got when you received the pre-compiled binary under the GPL.
The distribution rights granted by the GPL for modified versions of the work are not unconditional. Copyleft is a play on the word Copyright and describes the practice of using copyright law to remove restrictions on distributing copies and modified versions When someone distributes a GPL'd work plus their own modifications, the requirements for distributing the whole work cannot be any greater than the requirements that are in the GPL.
This requirement is known as copyleft. It earns its legal power from the use of copyright on software programs. Copyright is a legal concept enacted by Governments, giving the creator of an original work of authorship Exclusive rights to control its distribution usually for Because a GPL work is copyrighted, a licensee has no right to redistribute it, not even in modified form (barring fair use), except under the terms of the license. Fair use is a doctrine in United States copyright law that allows limited use of copyrighted material without requiring permission from the rights holders such as use for One is only required to adhere to the terms of the GPL if one wishes to exercise rights normally restricted by copyright law, such as redistribution. Conversely, if one distributes copies of the work without abiding by the terms of the GPL (for instance, by keeping the source code secret), he or she can be sued by the original author under copyright law. In law a lawsuit is a civil action brought before a Court in which the party commencing the action the Plaintiff, seeks a legal or equitable remedy
Copyleft thus uses copyright law to accomplish the opposite of its usual purpose: instead of imposing restrictions, it grants rights to other people, in a way that ensures the rights cannot subsequently be taken away. It also ensures that unlimited redistribution rights are not granted, should any legal flaw (or "bug") be found in the copyleft statement. A software bug (or just “bug” is an error flaw mistake Failure, fault or “undocumented feature” in a Computer program that prevents it
Many distributors of GPL'ed programs bundle the source code with the executables. In Computing, an executable (file causes a computer "to perform indicated tasks according to encoded instructions," as opposed to a file that only contains An alternative method of satisfying the copyleft is to provide a written offer to provide the source code on a physical medium (such as a CD) upon request. In practice, many GPL'ed programs are distributed over the Internet, and the source code is made available over FTP. The Internet is a global system of interconnected Computer networks For Internet distribution, this complies with the license.
Copyleft applies only when a person seeks to redistribute the program. One is allowed to make private modified versions, without any obligation to divulge the modifications as long as the modified software is not distributed to anyone else. Note that the copyleft applies only to the software and not to its output (unless that output is itself a derivative work of the program); for example, a public web portal running a modified derivative of a GPL'ed content management system is not required to distribute its changes to the underlying software. A content management system ( CMS) is a computer application used to create edit manage and publish content in a consistently organized fashion
The GPL was designed as a license, rather than a contract. The verb license or grant license means to give permission The noun license is the document demonstrating that permission A contract is an exchange of promises between two or more parties to do or refrain from doing an act which is enforceable in a court of law  In some Common Law jurisdictions, the legal distinction between a license and a contract is an important one: contracts are enforceable by contract law, whereas licenses are enforced under copyright law. Common law refers to law and the corresponding legal system developed through decisions of courts and similar tribunals rather than through legislative statutes or executive A contract is an exchange of promises between two or more parties to do or refrain from doing an act which is enforceable in a court of law Copyright is a legal concept enacted by Governments, giving the creator of an original work of authorship Exclusive rights to control its distribution usually for However, this distinction is not useful in the many jurisdictions where there are no differences between contracts and licenses, such as Civil Law systems. Civil law or Romano-Germanic law or Continental law is the predominant system of law in the world. 
Those who do not agree to the GPL's terms and conditions do not have permission, under copyright law, to copy or distribute GPL licensed software or derivative works. However, they may still use the software however they like.
The text of the GPL is itself copyrighted, and the copyright is held by the Free Software Foundation (FSF). The Free Software Foundation ( FSF) is a Non-profit corporation founded by Richard Stallman on 4 October 1985 to support the Free software movement However, the FSF does not hold the copyright for a work released under the GPL, unless an author explicitly assigns copyrights to the FSF (which seldom happens except for programs that are part of the GNU project). GNU ( pronounced) is a computer Operating system composed entirely of Free software. Only the individual copyright holders have the authority to sue when a license violation takes place.
The FSF permits people to create new licenses based on the GPL, as long as the derived licenses do not use the GPL preamble without permission. This is discouraged, however, since such a license is generally incompatible with the GPL.  (See the GPL FAQ for more information. )
Other licenses created by the GNU project include the GNU Lesser General Public License and the GNU Free Documentation License. The GNU Lesser General Public License (formerly the GNU Library General Public License) or LGPL is a Free software license published by the Free Software The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software
A key dispute related to the GPL is whether or not non-GPL software can dynamically link to GPL libraries. In Computer science, a library is a collection of Subroutines used to develop Software. The GPL is clear in requiring that all derivative works of GPL'ed code must themselves be GPL'ed. In Copyright law, a derivative work is an expressive creation that includes major basic copyrighted aspects of an original previously created first work However, it is not clear whether an executable that dynamically links to a GPL code should be considered a derivative work. The free/open-source software community is split on this issue. The FSF asserts that such an executable is indeed a derivative work if the executable and GPL code "make function calls to each other and share data structures," with others agreeing, while some (e. g. Linus Torvalds) agree that dynamic linking can create derived works but disagree over the circumstances. Linus Benedict Torvalds ( ˈtuːrvalds born December 28 1969 in Helsinki, Finland) is a Finnish software engineer  On the other hand, some experts have argued that the question is still open: one Novell lawyer has written that dynamic linking not being derivative "makes sense" but is not "clear-cut," and Lawrence Rosen has claimed that a court of law would "probably" exclude dynamic linking from derivative works although "there are also good arguments" on the other side and "the outcome is not clear" (on a later occasion, he argued that "market-based" factors are more important than the linking technique). Novell Inc ( is a global Software Corporation based in the United States specializing in enterprise operating systems such as SUSE Lawrence Rosen (also Larry Rosen is an attorney and computer specialist This is ultimately a question not of the GPL per se, but of how copyright law defines derivative works. In Galoob v. Nintendo the Ninth Circuit Court of Appeals defined a derivative work as having "'form' or permanence" and noted that "the infringing work must incorporate a portion of the copyrighted work in some form," but there have been no clear court decisions to resolve this particular conflict. Lewis Galoob Toys Inc v Nintendo of America Inc ( Ninth Circuit Court of Appeals, 1992) was a court case which established the rights of users The US Court of Appeals for the Ninth Circuit is a federal court with Appellate jurisdiction over the district courts in the following districts
Since there is no record of anyone circumventing the GPL by dynamic linking and contesting when threatened with lawsuits by the copyright holder, the restriction appears de facto enforceable even if not yet proven de jure.
In 2002, MySQL AB sued Progress NuSphere for copyright and trademark infringement in United States district court. The United States District Court for the District of Massachusetts is the Federal district court whose jurisdiction is the Commonwealth of Massachusetts, USA NuSphere had allegedly violated MySQL's copyright by linking code for the Gemini table type into the MySQL server. After a preliminary hearing before Judge Patti Saris on February 27, 2002, the parties entered settlement talks and eventually settled. Events 1560 - The Treaty of Berwick, which would expel the French from Scotland, is signed by England and the Congregation See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. At the hearing, Judge Saris "saw no reason" that the GPL would not be enforceable. 
In August 2003, the SCO Group stated that they believed the GPL to have no legal validity, and that they intended to take up lawsuits over sections of code supposedly copied from SCO Unix into the Linux kernel. The SCO Group Inc ( TSG, informally SCO;) is a software company formerly called Caldera Systems and Caldera International. Linux is an operating system kernel used by a family of Unix-like Operating systems These are popularly termed Linux operating systems and This was a problematic stand for them, as they had distributed Linux and other GPL'ed code in their Caldera OpenLinux distribution, and there is little evidence that they had any legal right to do so except under the terms of the GPL. Caldera OpenLinux is a defunct Linux distribution that was created by the former Caldera Systems (now SCO Group) corporation For more information, see SCO-Linux controversies and SCO v. IBM. The SCO-Linux controversies are a series of legal and public disputes between the Software company SCO Group (SCO and various Linux vendors and users SCO v IBM is a civil Lawsuit in the United States District Court of Utah.
In April 2004 the netfilter/iptables project was granted a preliminary injunction against Sitecom Germany by Munich District Court after Sitecom refused to desist from distributing Netfilter's GPL'ed software in violation of the terms of the GPL. Netfilter is a Framework that provides a set of hooks within the Linux kernel for intercepting and manipulating network packets. An injunction is an Equitable remedy in the form of a Court order, whereby a party is required to do or interact with in certain ways all right or to refrain from Munich (München; Minga is the capital city of Bavaria, Germany. On July 2004 , the German court confirmed this injunction as a final ruling against Sitecom.  The court's justification for its decision exactly mirrored the predictions given earlier by the FSF's Eben Moglen:
This ruling was important because it was the first time that a court had confirmed that violating terms of the GPL was an act of copyright violation. However, the case was not as crucial a test for the GPL as some have concluded. In the case, the enforceability of GPL itself was not under attack. Instead, the court was merely attempting to discern if the license itself was in effect.
In May of 2005, Daniel Wallace filed suit against the Free Software Foundation (FSF) in the Southern District of Indiana, contending that the GPL is an illegal attempt to fix prices at zero. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Wallace v International Business Machines Corp et al 467 F3d 1104 was a significant case in the development of Free software. The Free Software Foundation ( FSF) is a Non-profit corporation founded by Richard Stallman on 4 October 1985 to support the Free software movement The US District Court for the Southern District of Indiana was created in 1928 by an act of Congress that split Indiana into two separate districts The suit was dismissed in March 2006, on the grounds that Wallace had failed to state a valid anti-trust claim; the court noted that "the GPL encourages, rather than discourages, free competition and the distribution of computer operating systems, the benefits of which directly pass to consumers. " Wallace was denied the possibility of further amending his complaint, and was ordered to pay the FSF's legal expenses.
On September 8, 2005, Seoul Central District Court ruled that GPL has no legal relevance concerning the case dealing with trade secret derived from GPL-licensed work. A trade secret is a Formula, practice, Process, Design, instrument, Pattern, or compilation of Information which  Defendants argued that since it is impossible to maintain trade secret while being compliant with GPL and distributing the work, they aren't in breach of trade secret. This argument was considered without ground.
On September 6, 2006, the gpl-violations.org project prevailed in court litigation against D-Link Germany GmbH regarding D-Link's inappropriate and copyright infringing use of parts of the Linux Operating System Kernel. The GPL-Violationsorg is a not-for-profit project founded and led by Harald Welte in 2004  The judgment finally provided the on-record, legal precedent that the GPL is valid and legally binding, and that it will stand up in German court. 
In late 2007, the developers of BusyBox and the Software Freedom Law Center embarked upon a program to gain GPL compliance from distributors of BusyBox in embedded systems, suing those who would not comply. BusyBox is a Software application which provides many standard Unix tools much like the larger (but more capable GNU Core Utilities. The Software Freedom Law Center (SFLC is an organization that provides legal representation and related services to protectand advance Free software / Open source An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints These were claimed to be the first US uses of courts for enforcement of GPL obligations. See BusyBox#GPL lawsuits. BusyBox is a Software application which provides many standard Unix tools much like the larger (but more capable GNU Core Utilities.
Many of the most common free software licenses, such as the original MIT/X license, the BSD license (in its current 3-clause form), and the LGPL, are "GPL-compatible". The MIT License is a Free software license originating at the Massachusetts Institute of Technology (MIT used by the MIT X Consortium. BSD licenses represent a family of Permissive free software licences. The GNU Lesser General Public License (formerly the GNU Library General Public License) or LGPL is a Free software license published by the Free Software License compatibility refers to the problem with licenses of software packages which can contain contradictory requirements rendering it impossible to combine Source code That is, their code can be combined with a program under the GPL without conflict (the new combination would have the GPL applied to the whole). However, some free/open source software licenses are not GPL-compatible. Many GPL proponents have strongly advocated that free/open source software developers use only GPL-compatible licenses, because doing otherwise makes it difficult to reuse software in larger wholes. Note that this issue only arises in concurrent use of licenses which impose conditions on their manner of combination. Some licenses, such as the BSD license, impose no conditions on the manner of their combination.
Also see the list of FSF approved software licenses for examples of compatible and incompatible licenses. The following is a list of Software licences which Free Software Foundation (FSF has approved as complying with their Free Software Definition.
A number of businesses use dual-licensing to distribute a GPL version and sell a proprietary license to companies wishing to combine the package with proprietary code, using dynamic linking or not. Dual-licensing is the practice of distributing Software under two different sets of terms and conditions Proprietary software is Computer software on which the producer has set restrictions on use private modification copying, or republishing. Examples of such companies include MySQL AB, Trolltech (Qt toolkit), Namesys (ReiserFS) and Red Hat (Cygwin). MySQL AB (founded 1995 acquired by Sun Microsystems 2008 was dual headquartered in Uppsala, Sweden and Cupertino, California Qt (pronounced "cute" by its creators is a Cross-platform application development framework widely used for the development of GUI programs (in which Namesys is a California Corporation responsible for the design and implementation of the ReiserFS and Reiser4 filesystems ReiserFS is a general-purpose journaled Computer File system designed and implemented by a team at Namesys led by Hans Reiser In Computing, Red Hat Inc ( is a company dedicated to Free and open source software, and a major Linux distribution vendor Cygwin (ˈsɪɡwɪn is a collection of tools originally developed by Cygnus Solutions to provide in Microsoft Windows a command line and programming interface familiar
In 2001 Microsoft CEO Steve Ballmer referred to Linux as "a cancer that attaches itself in an intellectual property sense to everything it touches. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer A chief executive officer ( CEO) or chief executive is typically the highest-ranking corporate officer ( executive) or administrator Steve Anthony Ballmer (born March 24 1956 is an American Businessman. " Critics of Microsoft claim that the real reason Microsoft dislikes the GPL is that the GPL resists proprietary vendors' attempts to "embrace, extend and extinguish". " Embrace extend and extinguish," also known as " Embrace extend and exterminate," is a phrase that the U  Microsoft has released Microsoft Windows Services for UNIX which contains GPL-licensed code. Microsoft Windows Services for UNIX ( SFU) is a software package produced by Microsoft which provides a Unix subsystem and other parts of a full Unix In response to Microsoft's attacks on the GPL, several prominent Free Software developers and advocates released a joint statement supporting the license. 
The GPL has been described as being "viral" by many of its critics because the GPL only allows conveyance of whole programs, which means that programmers are not allowed to convey programs that link to libraries having GPL-incompatible licenses. Copyleft is a play on the word Copyright and describes the practice of using copyright law to remove restrictions on distributing copies and modified versions A GPL linking exception modifies the GNU General Public License (GPL to create a new modified license The so-called "viral" effect of this is that under such circumstances disparately licensed software cannot be combined unless one of the licenses is changed. Although theoretically either license could be changed, in the "viral" scenario the GPL cannot be practically changed (because the software may have so many contributors, some of whom will likely refuse), whereas the license of the other software can be practically changed.
This is part of a philosophical difference between the GPL and permissive free software licenses such as the BSD-style licenses, which do not put such a requirement on modified versions. A free software licence is a Software licence which grants recipients rights to modify and redistribute the Software which would otherwise be prohibited by Copyright BSD licenses represent a family of Permissive free software licences. While proponents of the GPL believe that free software should ensure that its freedoms are preserved all the way from the developer to the user, others believe that intermediaries between the developer and the user should be free to redistribute the software as non-free software. More specifically, the GPL requires that redistribution occur subject to the GPL, whereas more "permissive" licenses allow redistribution to occur under licenses more restrictive than the original license.
While the GPL does allow commercial distribution of GPL software, the market price will settle near the price of distribution—near zero—since the purchasers may redistribute the software and its source code for their cost of redistribution. This could be seen to inhibit commercial use of GPL'ed code by others wishing to use that code for proprietary purposes—if they don't wish to avail themselves of GPL'ed code, they will have to re-implement it themselves. Microsoft has included anti-GPL terms in their open source software.
In addition, the FreeBSD project has stated that "a less publicized and unintended use of the GPL is that it is very favorable to large companies that want to undercut software companies. FreeBSD is a Unix-like free Operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD branch through In other words, the GPL is well suited for use as a marketing weapon, potentially reducing overall economic benefit and contributing to monopolistic behavior".  It's not clear that there are any cases of this happening in practice, however.
The GPL has no indemnification clause explicitly protecting maintainers and developers from litigation resulting from unscrupulous contribution. An indemnity is a sum paid by A to B by way of compensation for a particular loss suffered by B. (If a developer submits existing patented or copyright work to a GPL project claiming it as their own contribution, all the project maintainers and even other developers can be held legally responsible for damages to the copyright or patent holder. ) Lack of indemnification is one criticism that lead Mozilla to create the Mozilla Public License rather than use the GPL or LGPL. The Mozilla Public License (MPL is a free and Open source Software license. However, Mozilla later relicensed their work under a GPL/LGPL/MPL triple license, due to problems with the GPL-incompatibility of the MPL.
Some software developers have found the extensive scope of the GPL to be too restrictive. For example, Bjørn Reese and Daniel Stenberg describe how the downstream effects of the GPL on later developers creates a "quodque pro quo" (Latin, "Everything in return for something"). For that reason, in 2001 they abandoned the GPLv2 in favor of less restrictive copyleft licenses. 
A more specific example of the downstream effects of the GPL can be observed through the frame of incompatible licenses. Sun Microsystems' ZFS, because it is licensed under the GPL-incompatible CDDL and covered by several Sun patents, cannot link to the GPL-licensed linux kernel. 
Some have also argued that the GPL could, and should, be shorter.