GNU Lesser General Public License

GNU Lesser General Public License. The GNU Lesser General Public License is a widely used free software license published by the Free Software Foundation. It is designed to permit a greater degree of linking flexibility with non-free software than its stronger counterpart, the GNU General Public License, while still preserving certain copyleft freedoms for the licensed work itself. Often used for software libraries, it aims to encourage the adoption of free software components in both free and proprietary development projects.

History and development

The license was originally published in 1991 as the GNU Library General Public License, with version 2.0 coinciding with that of the GNU General Public License. The name was changed in 1999 to better reflect its intended use, as the Free Software Foundation felt the term "library" was misleading and encouraged overuse in contexts where the stronger GNU General Public License was more appropriate. The current version, LGPLv3, was released in 2007 alongside GPLv3 to address new legal challenges, such as tivoization and compatibility with other licenses like the Apache License. Key figures in its evolution include Richard Stallman and the legal team at the Free Software Foundation, who drafted it to serve as a strategic compromise within the broader free software movement.

Terms and conditions

The license grants users the freedom to run, study, share, and modify the software. Its core requirement is that modifications to the licensed work itself must be released under the same terms, but it permits linking with modules that are under other licenses, including proprietary ones. A critical provision allows a combined work to be distributed under terms of the user's choice, provided that mechanisms for reverse-engineering to debug modifications are offered, such as through the use of a suitable shared library mechanism. It also includes explicit patent grants from contributors and contains provisions against DRM restrictions, aligning with the updates in GPLv3. These terms are enforced under copyright law, similar to other licenses from the Free Software Foundation.

Compatibility with other licenses

It is generally compatible with the GNU General Public License, as works under it can be relicensed under the GNU General Public License if desired. However, its compatibility with other popular licenses is more nuanced; it is one-way compatible with the Apache License 2.0, as Apache-licensed code can be incorporated into an LGPL-licensed project. There are complexities with the Mozilla Public License and the Eclipse Public License, often requiring careful analysis for combined distribution. The Free Software Foundation maintains detailed compatibility matrices, and projects like GNU Classpath have navigated these issues to ensure interoperability within the Java ecosystem and with systems governed by the Berkeley Software Distribution license.

Usage and adoption

It is extensively adopted for critical software libraries and frameworks where developer freedom to link with proprietary code is a priority. Prominent projects using it include the GTK graphical toolkit, the GNU C Library, and the OpenOffice.org suite (in its earlier iterations). Many libraries within the GNOME desktop environment and the MediaWiki software platform are also distributed under it. This strategic adoption by major projects like Mozilla Firefox (for certain components) and the LibreOffice project has cemented its role in the ecosystem, encouraging its use in commercial products from companies like Red Hat and IBM while still advancing the goals of the free software movement.

Criticisms and controversies

A primary criticism, notably from the Free Software Foundation itself, is that its weak copyleft nature can undermine the spread of free software by making it too easy to incorporate into proprietary products. Some developers, including those from the Open Source Initiative, argue that its complexity and specific linking requirements create legal uncertainty compared to more permissive licenses like the MIT License or Berkeley Software Distribution license. Debates have occurred within communities like KDE and Debian regarding whether it provides sufficient protection for software freedom. Furthermore, the anti-tivoization clauses in version 3.0 were controversial, leading some projects, including the Linux kernel community, to reject its adoption in favor of version 2.0.

Comparison with the GNU General Public License

The fundamental difference lies in the strength of their copyleft provisions; the GNU General Public License is a strong copyleft license that requires the entire combined work to be distributed under its terms, whereas the weaker copyleft of the other license applies primarily to the licensed library itself. This makes the latter more suitable for software libraries intended for widespread use, as seen with the GNU C Library, while the former is preferred for complete applications like the GNU Compiler Collection. Both licenses share the same philosophical foundation from the Free Software Foundation and include similar clauses regarding patent retaliation and freedom from DRM, but their legal implications for linking and distribution create distinct strategic choices for projects like LibreOffice versus the GNU Emacs editor. Category:Free software licenses Category:GNU Project Category:1991 software