Lesser GNU Public License

Lesser GNU Public License
Name	Lesser GNU Public License
Abbreviation	LGPL
Author	Richard Stallman / Free Software Foundation
Initial release	1991
Latest release	3.0 (2007)
Os	GNU / Linux / cross-platform
License	Free Software Foundation copyleft

Lesser GNU Public License

The Lesser GNU Public License is a widely used free software license drafted by Richard Stallman and published by the Free Software Foundation for the GNU Project software ecosystem, intended to allow linking of proprietary and open-source components. It provides a middle ground between strong copyleft terms like those of GNU General Public License and permissive terms exemplified by the MIT License and the BSD licenses, enabling reuse in diverse projects while preserving user freedoms for covered libraries.

Overview

The license permits redistribution and modification of covered libraries while allowing them to be linked with nonfree programs, distinguishing it from the GNU General Public License and aligning it with practical use in Linux Kernel-adjacent projects, GIMP-related plugins, and GNOME components. It originated to address concerns from organizations such as Red Hat, Debian, Canonical and companies like IBM and Oracle Corporation that required a balance between Free Software Foundation ideals and commercial software development. The license’s permissive linking rules influenced ecosystems including Qt, SDL, wxWidgets and other portable libraries used by projects like LibreOffice, MySQL, PostgreSQL, Apache HTTP Server integrations, and Python extension modules.

History and Development

The initial version emerged in 1991 amid debates between Richard Stallman and contributors from organizations including X Consortium, Netscape Communications Corporation, and Sun Microsystems about compatibility with proprietary software and library linking. Subsequent revisions, including the 2.1 and the significant LGPLv3 (2007) release, were driven by interactions with standards bodies and legal developments involving European Commission initiatives, World Intellectual Property Organization practices, and litigation trends such as cases referenced in United States Court of Appeals for the Federal Circuit decisions. Key participants in drafting and commentary included Stuart Feldman, Eric S. Raymond, representatives from Red Hat and Mozilla Foundation, and counsel experienced with Software Freedom Law Center matters. The evolution reflected responses to issues raised by projects like KDE and OpenOffice.org and by companies such as Google and Microsoft that navigated open-source dependencies.

Terms and Licensing Provisions

Core provisions require that modifications to the covered library be distributed under the same license, while allowing non-(L)GPL programs to link to the library without subjecting their entire codebase to the same copyleft terms, unlike the GNU General Public License. The license includes source availability obligations inspired by precedents in Berkeley Software Distribution history and includes patent clauses shaped by agreements and confrontations involving entities like IBM, Sun Microsystems, Nokia, Apple Inc., and Samsung. LGPLv3 incorporated compatibility with Affero General Public License debates and addressed concerns raised by European Union jurisprudence and Free Software Foundation Europe. It defines conveyance, installation information, and anti-tivoization language adjustments influenced by disputes involving Tivo-like devices and vendors such as Cisco Systems and Motorola. The text also distinguishes static linking from dynamic linking in ways that informed integration strategies for toolchains from GCC and LLVM.

Compatibility with Other Licenses

Compatibility has been a focal point, with the license explicitly permitting linking with code under permissive licenses such as the MIT License, the BSD licenses, and the Apache License 2.0 under certain versions and conditions, while maintaining incompatibilities with some proprietary licenses and earlier copyleft texts. Interactions with the GPLv2 and GPLv3 and relicensing concerns involve projects like Mozilla Firefox, Chromium, Android, and database ecosystems including MariaDB and SQLite. Legal interpretations have been informed by precedent from jurisdictions including the United Kingdom, the United States, Germany, and France, and by policy positions from organizations like Open Source Initiative and Free Software Foundation Europe.

Adoption and Notable Use Cases

The license has been adopted by numerous libraries and toolkits used across commercial and open-source projects, including glibc, libpng, zlib-adjacent modules, FFmpeg components in certain builds, and parts of GNOME and KDE stacks. Enterprise usage spans vendors such as Red Hat, SUSE, Canonical, Oracle Corporation, IBM, and Google, which have integrated LGPL-licensed libraries into products like Android and Chromebook ecosystems. The license has enabled contributions to major applications like LibreOffice, GIMP, Blender, OpenCV, and scientific tools used at institutions including CERN, NASA, MIT, Stanford University, and University of California, Berkeley.

Criticisms and Legal Issues

Critics argue the license’s linking exceptions create ambiguity around static linking, combined works, and distribution obligations, concerns raised in discussions involving Software Freedom Conservancy, Electronic Frontier Foundation, and legal scholars from Harvard Law School and Stanford Law School. High-profile disputes and clarifications have involved companies such as Cisco Systems, Google, Apple Inc., and Microsoft, and have prompted commentary in forums hosted by Open Source Initiative and events like FOSDEM and LibrePlanet. Debates continue over patent retaliation clauses, enforcement strategies used by organizations including Free Software Foundation and Software Freedom Law Center, and international enforcement complexities seen in rulings from courts in Germany and the United States District Court for the Northern District of California.

Category:Free and open-source software licenses