GNU General Public License

GNU General Public License. It is a widely used free software license that guarantees end users the freedom to run, study, share, and modify the software. Created by Richard Stallman for the GNU Project, it was the first copyleft license for general use, ensuring that all derivative works remain under the same terms. The license is formally maintained and published by the Free Software Foundation and has become a cornerstone of the open-source software movement, applied to projects like the Linux kernel and WordPress.

History and versions

The first version was drafted by Richard Stallman in 1989, with legal advice from Eben Moglen, to protect software developed for the GNU Project. Version 2, released in 1991, became profoundly influential after its adoption by Linus Torvalds for the Linux kernel, addressing issues of liberty and compatibility with other licenses. The lengthy process for Version 3 began in 2005, involving public consultations and debates over issues like tivoization and software patents, culminating in its final release in 2007 by the Free Software Foundation. While many projects like the GNU Compiler Collection adopted GPLv3, others, most notably the Linux kernel, have remained on the earlier version 2.

Terms and conditions

The core legal mechanism is copyleft, which requires that any distributed modified versions or works containing GPL-licensed code must be released under the same license terms, preserving user freedoms. It grants recipients the essential freedoms to use the software for any purpose, to study its source code, to redistribute copies, and to distribute modified versions. Key obligations include providing the complete corresponding source code when distributing binaries and ensuring all downstream recipients receive these same rights and access. The license explicitly states that no additional restrictions can be placed on these rights, a principle tested in cases like the SCO-Linux controversies.

Compatibility and licensing

Compatibility with other free software licenses is a complex area; it is generally compatible with permissive licenses like the MIT License and BSD licenses, as their code can be relicensed under it, but combining with other strong copyleft licenses like the GNU Affero General Public License is more nuanced. The Free Software Foundation maintains a list of compatible licenses, and projects like Qt have navigated dual-licensing models involving it and commercial licenses. A significant compatibility challenge arose with the Apache License 2.0, which was resolved for GPLv3 but not for GPLv2, affecting projects within the Apache Software Foundation.

Impact and adoption

Its adoption catalyzed the growth of the free software ecosystem, with foundational projects like the GNU operating system, Linux kernel, and Git using it, influencing the development model of organizations like the Apache Software Foundation. It has shaped business models around open-source software, with companies like Red Hat and Canonical building successful enterprises by providing support and services for GPL-licensed software. The license has been a key tool in legal defenses against proprietary encroachment, notably in high-profile cases like those involving SCO Group and MySQL AB.

Legal interpretation and enforcement

Enforcement has historically been handled by the copyright holders, often with support from the Free Software Foundation and organizations like the Software Freedom Law Center, aiming for compliance through negotiation rather than litigation. Landmark legal cases, such as those involving Harald Welte and Sitecom, have affirmed its validity and enforceability in courts in Germany and the United States. The concept of "linking" and what constitutes a derivative work under the license, as debated in contexts like the GNU Lesser General Public License, remains a critical area for legal interpretation. Ongoing discussions about its application in new domains, such as SaaS and artificial intelligence, continue to test its legal boundaries.

Category:Free software licenses Category:GNU Project Category:1989 software