License library / Copyleft software
GNU Lesser General Public License v2.1 only
Use the library in any program, including proprietary ones; changes to the library itself, when distributed, stay under the LGPL with source, and users must be able to relink a modified library.
SPDX LGPL-2.1-only Version 2.1 Official text
Uses at a glance
| commercial use | Permitted |
|---|---|
| production deployment | Permitted |
| modification / derivatives | Permitted |
| redistribution | Permitted |
| sublicensing | Prohibited |
| AI model training | Needs human review |
| inference-time use (RAG, prompts, generation) | Permitted |
Why some uses need review
AI model training. The license grants broad rights but attaches conditions (such as keeping notices) to copies and adaptations. Whether a trained model, or its output, is a copy or adaptation that carries those conditions is legally unsettled, and in some places training may fall under an exception such as fair use. A human reviewer should confirm this use for your case.
Duties
- give attribution / keep the notice
- license notice
- state changes
- release distributed derivatives under the same license
- provide source code with distributed derivatives
Notes
- The copyleft duties apply to the library and modified versions of it, not to an application that only links to it (section 5).
- Each recipient receives a license from the original licensor; sublicensing is not allowed (section 10).
Resources under this license
No resource in the registry is published under this license yet.
For agents
curl -s https://www.rightshold.com/v1/licenses/check -H 'content-type: application/json' \
-d '{"license":"LGPL-2.1-only","intended_use":{"commercial_use":true,"deployment":true}}'Reading version 2026-10-09 by the Rightshold rights desk; reference hash e9a574ec8659a9afeab237b839304d4acadae69ff6aa3c9d88a8e2de1317f722 identifies this license version. The license text governs; this is not legal advice.