GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses, or copyleft, that guarantee end users the four freedoms to run, study, share, and modify the software.[7] The license was the first copyleft for general use, and was originally written by Richard Stallman, the founder of the Free Software Foundation (FSF), for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition.[8] The licenses in the GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. It is more restrictive than the Lesser General Public License, and even further distinct from the more widely-used permissive software licenses BSD, MIT, and Apache.
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Historically, the GPL license family has been one of the most popular software licenses in the free and open-source software (FOSS) domain.[7][9][10][11][12] Prominent free software programs licensed under the GPL include the Linux kernel and the GNU Compiler Collection (GCC). David A. Wheeler argues that the copyleft provided by the GPL was crucial to the success of Linux-based systems, giving the programmers who contributed to the kernel the assurance 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.[13]
In 2007, the third version of the license (GPLv3) was released to address some perceived problems with the second version (GPLv2) which were discovered during the latter's long-time usage.
To keep the license current, the GPL license includes an optional "any later version" clause, allowing users to choose between the original terms or the terms in new versions as updated by the FSF. Software projects licensed with the optional "or later" clause include the GNU Project, while the Linux kernel, for instance, is licensed under GPLv2 only.
The "or any later version" clause is sometimes known as a "lifeboat clause" since it allows combinations between different versions of GPL-licensed software to maintain compatibility.
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Published
25 February 1989
June 1991
29 June 2007
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Derivations[edit]
The text of the GPL is itself copyrighted, and the copyright is held by the Free Software Foundation.
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 might be incompatible with the GPL[61] and causes a perceived license proliferation.
Other licenses created by the GNU project include the GNU Lesser General Public License, GNU Free Documentation License, and GNU Affero General Public License.
The text of the GPL is not itself under the GPL. The license's copyright disallows modification of the license. Copying and distributing the license is allowed since the GPL requires recipients to get "a copy of this License along with the Program".[62] According to the GPL FAQ, anyone can make a new license using a modified version of the GPL as long as they use a different name for the license, do not mention "GNU", and remove the preamble, though the preamble can be used in a modified license if permission to use it is obtained from the Free Software Foundation (FSF).[63]
Text and other media[edit]
It is possible to use the GPL for text documents instead of computer programs, or more generally for all kinds of media, if it is clear what constitutes the source code (defined as "the preferred form of the work for making changes in it").[110] For manuals and textbooks, though, the FSF recommends the GNU Free Documentation License (GFDL) instead, which it created for this purpose.[111] Nevertheless, the Debian developers recommended (in a resolution adopted in 2006) to license documentation for their project under the GPL, because of the incompatibility of the GFDL with the GPL (text licensed under the GFDL cannot be incorporated into GPL software).[112][113] Also, the FLOSS Manuals foundation, an organization devoted to creating manuals for free software, decided to eschew the GFDL in favor of the GPL for its texts in 2007.[114]
If the GPL is used for computer fonts, any documents or images made with such fonts might also have to be distributed under the terms of the GPL. This is not the case in countries that recognize typefaces (the appearance of fonts) as being a useful article and thus not eligible for copyright, but font files as copyrighted computer software (which can complicate font embedding, since the document could be considered 'linked' to the font; in other words, embedding a vector font in a document could force it to be released under the GPL, but a rasterized rendering of the font would not be subject to the GPL). The FSF provides an exception for cases where this is not desired.[115]
Reception[edit]
Legal barrier to application stores[edit]
The GPL is incompatible with many application digital distribution systems, like the Mac App Store, and certain other software distribution platforms (on smartphones as well as PCs). The problem lies in the right "to make a copy for your neighbour", as this right is violated by digital rights management systems embedded within the platform to prevent copying of paid software. Even if the application is free in the application store in question, it might result in a violation of that application store's terms.[143]
There is a distinction between an app store, which sells DRM-restricted software under proprietary licenses, and the more general concept of digital distribution via some form of online software repository. Virtually all modern Unix systems and Linux distributions have application repositories, including NetBSD, FreeBSD, Ubuntu, Fedora, and Debian. These specific application repositories all contain GPL-licensed software apps, in some cases even when the core project does not permit GPL-licensed code in the base system (for instance OpenBSD[144]). In other cases, such as the Ubuntu App Store, proprietary commercial software applications and GPL-licensed applications are both available via the same system; the reason that the Mac App Store (and similar projects) is incompatible with GPL-licensed apps is not inherent in the concept of an app store, but is rather specifically due to Apple's terms-of-use requirement[143] that all apps in the store utilize Apple DRM restrictions. Ubuntu's app store does not demand any such requirement: "These terms do not limit or restrict your rights under any applicable open source software licenses."[145]
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