GNU General Public License
GNU General Public License
The GNU General Public License (often abbreviated GNU GPL or simply GPL) is a widely used free software license originally written by Richard Stallman for the GNU Project. It is the primary license of the Linux kernel, many GNU tools, and thousands of other programs. The GPL is a copyleft license, meaning that derivative works must be distributed under the same license terms, ensuring that freedom to use, modify, and share the software is preserved.
History
The first version of the GPL (GPLv1) was released in February 1989 by the Free Software Foundation (FSF). It was designed to replace the earlier GNU Emacs General Public License, which had a similar copyleft clause but applied only to Emacs. GPLv2 followed in June 1991, adding the "Liberty or Death" clause (Section 7) that allowed licensors to add restrictions if required by patent or other legal conflicts. The current version, GPLv3, was released on 29 June 2007 after a lengthy public consultation process. It addresses software patent retaliation, tivoization, and Digital Restrictions Management (DRM).
Key Features
- Copyleft: Anyone who distributes a modified version of the software must release it under the same GPL license, including source code.
- Source code availability: Distributors must provide the complete corresponding source code, either with the binary or upon request.
- No additional restrictions: The license prohibits further legal restrictions (e.g., patent agreements) that would limit the user's freedom to run, modify, or share the program.
- Compatibility: GPLv3 is designed to be interoperable with Apache License 2.0 and GNU Affero General Public License, while GPLv2 is often considered incompatible with the Apache license.
Versions
- GPLv1 – 1989. Established the copyleft principle.
- GPLv2 – 1991. Added Section 7 to handle patent and other legal conflicts. Used by the Linux kernel.
- GPLv3 – 2007. Extended protection against anti-circumvention laws and patent retaliation clauses.
Adoption
The GPL is one of the most popular free software licenses. Major projects under the GPL include Linux kernel (GPLv2 only), WordPress, Git (GPLv2), and MySQL (dual-licensed). The FSF maintains a list of GPL-compatible licenses and a GNU Free Documentation License for documentation.