GPLcopyleft

GPLcopyleft refers to the family of copyleft licenses associated with the GNU General Public License (GPL). It embodies the principle that the freedom to use, study, modify, and share software should extend to all modified and derivative works. The term is not a single license but a description of the copyleft approach used by the GPL and its variants.

Core idea: when distributed, software licensed under the GPL requires that source code be made available and that the same licensing terms apply to any modified versions or combined works that include GPL-covered components. This reciprocal obligation is designed to ensure that future users retain the same freedoms.

Versions and scope: The GPL has evolved through multiple versions, notably GPLv2 and GPLv3. GPLv3 adds stronger protections against anti-circumvention devices (tivoization), clarifies patent rights, and improves license compatibility with other open licenses. GPLv2 is simpler and has been argued to permit certain distribution practices not allowed under GPLv3.

Related licenses: The GPL family also includes licenses with weaker copyleft, such as the LGPL, and licenses that extend copyleft to network use, such as the AGPL. These licenses are often discussed in relation to GPLcopyleft when designing software ecosystems.

Impact and criticism: GPLcopyleft licenses have been instrumental in preserving software freedom and enabling collaborative development. Critics argue that strong copyleft can complicate integration with proprietary software or mixed-license projects, leading some developers to prefer permissive licenses.

Examples: The Linux kernel is distributed under GPLv2, illustrating widespread use of GPL-style copyleft. Many GNU utilities and applications are released under GPL licenses as well.