GNU Lesser General Public License

GNU Lesser General Public License

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Published	1991; 33 years ago (1991)
SPDX identifier	LGPL-3.0-or-later LGPL-3.0-only LGPL-2.1-or-later LGPL-2.1-only LGPL-2.0-or-later LGPL-2.0-only
Debian FSG compatible	Yes[1]
FSF approved	Yes[2]
OSI approved	Yes[3]
GPL compatible	Yes[2]
Copyleft	Yes[2] (library or dynamic linking-based)
Linking from code with a different licence	Yes
Website	www.gnu.org/copyleft/lesser.html

The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own (even proprietary) software without being required by the terms of a strong copyleft license to release the source code of their own components. However, any developer who modifies an LGPL-covered component is required to make their modified version available under the same LGPL license. For proprietary software, code under the LGPL is usually used in the form of a shared library, so that there is a clear separation between the proprietary and LGPL components. The LGPL is primarily used for software libraries, although it is also used by some stand-alone applications.

The LGPL was developed as a compromise between the strong copyleft of the GNU General Public License (GPL) and more permissive licenses such as the BSD licenses and the MIT License. The word "Lesser" in the title shows that the LGPL does not guarantee the end user's complete freedom in the use of software; it only guarantees the freedom of modification for components licensed under the LGPL, but not for any proprietary components.