GNU Lesser General Public License v3.0

GNU Lesser General Public License v3.0

Weak Copyleft

LGPL-3.0 allows proprietary software to link against LGPL-licensed libraries without the proprietary code becoming GPL-licensed. However, modifications to the LGPL library itself must be released under LGPL-3.0, and users must be able to replace the LGPL library with a modified version.

The full text of the GNU Lesser General Public License v3.0 is available at https://www.gnu.org/licenses/lgpl-3.0.en.html.

The LGPL-3.0 is defined as an additional set of permissions on top of the GPL-3.0. It inherits all GPL-3.0 terms and adds exceptions for linking.

What this means

The LGPL-3.0 is a weak copyleft license designed for libraries. Key provisions:

• Linking exception: Proprietary applications can link to LGPL-3.0 libraries (statically or dynamically) without the application itself becoming GPL-licensed.
• Library modifications: If you modify the LGPL library’s source, the modified library must be released under LGPL-3.0.
• User freedom: End users must be able to replace the LGPL library with their own modified version (typically satisfied by dynamic linking or providing object files for relinking).
• Patent grant: Same as GPL-3.0 — contributors grant patent rights.

Where this applies

LGPL-3.0 is common in media processing libraries (FFmpeg components, audio codecs), GUI toolkits, and system libraries. When the KBVE monorepo links against an LGPL-3.0 library, the linking exception allows the surrounding proprietary application to remain under the EULA, while the LGPL library itself retains its copyleft obligations.