LGPL-3.0 vs Proprietary License

GNU Lesser General Public License v3.0 compared with Proprietary / commercial licence: what each licence allows, and whether code under one can be used in a project under the other. Results are generated by the open-source license compatibility checker.

Quick Answer

Compatibility is directional, so both directions are answered separately (distributed software):

LGPL-3.0 code in proprietary software

Compatible With Conditions

Using LGPL-3.0-licensed code in a proprietary project is generally possible if the listed conditions are met.

An application that uses an LGPL-3.0 library may be distributed under its own terms, including proprietary terms, when section 4 is met: typically by using the library as a replaceable shared library, giving notice of its use, and including the licence.

proprietary code in a project licensed under LGPL-3.0

Manual Review Required

Using Proprietary-licensed code in a project under LGPL-3.0 requires review of the actual licence terms.

The component is under proprietary terms. Whether it may be used, modified, redistributed, resold or white-labelled depends entirely on the specific licence agreement.

Key Differences

Type: LGPL-3.0: open source; Proprietary: proprietary.
OSI approved: LGPL-3.0: yes; Proprietary: no.
Commercial use: LGPL-3.0: permitted; Proprietary: depends on the licence agreement.
Modification: LGPL-3.0: permitted; Proprietary: depends on the licence agreement.
Distribution: LGPL-3.0: permitted; Proprietary: depends on the licence agreement.
Copyleft: LGPL-3.0: weak (library / module level); Proprietary: none.
Network-use (SaaS) clause: LGPL-3.0: no; Proprietary: depends on the licence agreement.
Source disclosure: LGPL-3.0: the library and changes to it; Proprietary: depends on the licence agreement.
Same licence for distributed changes: LGPL-3.0: yes; Proprietary: depends on the licence agreement.
Attribution / notices: LGPL-3.0: yes; Proprietary: depends on the licence agreement.
Mark modified files: LGPL-3.0: yes; Proprietary: depends on the licence agreement.
Express patent licence: LGPL-3.0: yes; Proprietary: depends on the licence agreement.
Patent termination clause: LGPL-3.0: yes; Proprietary: depends on the licence agreement.

Comparison Table

	LGPL-3.0	Proprietary
Type	Open source	Proprietary
OSI approved	Yes	No
Commercial use	Permitted	Depends on the licence agreement
Modification	Permitted	Depends on the licence agreement
Distribution	Permitted	Depends on the licence agreement
Copyleft	Weak (library / module level)	None
Network-use (SaaS) clause	No	Depends on the licence agreement
Source disclosure	The library and changes to it	Depends on the licence agreement
Same licence for distributed changes	Yes	Depends on the licence agreement
Attribution / notices	Yes	Depends on the licence agreement
Mark modified files	Yes	Depends on the licence agreement
Express patent licence	Yes	Depends on the licence agreement
Patent termination clause	Yes	Depends on the licence agreement
Trademark rights granted	Not addressed	Not addressed

Commercial Use

LGPL-3.0: permitted.
Proprietary: depends on the licence agreement.

LGPL-3.0 code in proprietary software: LGPL-3.0 permits commercial use. Commercial use, including selling copies, is allowed; the copyleft conditions still apply to how the code is distributed.
proprietary code in a project licensed under LGPL-3.0: The component is under proprietary terms. Whether it may be used, modified, redistributed, resold or white-labelled depends entirely on the specific licence agreement.

Proprietary Software

LGPL-3.0 code in closed-source commercial software

Compatible With Conditions

Using LGPL-3.0-licensed code in a proprietary project is generally possible if the listed conditions are met.

LGPL-3.0 code in closed-source commercial software: An application that uses an LGPL-3.0 library may be distributed under its own terms, including proprietary terms, when section 4 is met: typically by using the library as a replaceable shared library, giving notice of its use, and including the licence.

SaaS

Network-use clause: LGPL-3.0: no; Proprietary: depends on the licence agreement.

LGPL-3.0 code in a closed-source SaaS

Generally Compatible

Using LGPL-3.0-licensed code in a proprietary project is generally compatible in this scenario.

LGPL-3.0 copyleft conditions are triggered by distribution; this scenario does not include distribution.

LGPL-3.0 code in a closed-source SaaS: LGPL-3.0 has no network-use (SaaS) clause.

Modification

LGPL-3.0: permitted; modified files must be marked.
Proprietary: depends on the licence agreement.

Modifying LGPL-3.0 code used in closed-source software

Compatible With Conditions

Using LGPL-3.0-licensed code in a proprietary project is generally possible if the listed conditions are met.

Modifying LGPL-3.0 code used in closed-source software: LGPL-3.0 permits modification. LGPL-3.0 requires modified files to carry notices stating that they were changed.

Distribution

LGPL-3.0: permitted.
Proprietary: depends on the licence agreement.

LGPL-3.0 code in proprietary software: LGPL-3.0 permits distribution subject to its copyleft conditions.
proprietary code in a project licensed under LGPL-3.0: The component is under proprietary terms. Whether it may be used, modified, redistributed, resold or white-labelled depends entirely on the specific licence agreement.

Copyleft

LGPL-3.0: weak (library / module level) copyleft.
Proprietary: none copyleft.

LGPL-3.0 code in proprietary software: An application that uses an LGPL-3.0 library may be distributed under its own terms, including proprietary terms, when section 4 is met: typically by using the library as a replaceable shared library, giving notice of its use, and including the licence.
proprietary code in a project licensed under LGPL-3.0: Proprietary has no copyleft.

Source Disclosure

LGPL-3.0: the library and changes to it.
Proprietary: depends on the licence agreement.

LGPL-3.0 code in proprietary software: An application that uses an LGPL-3.0 library may be distributed under its own terms, including proprietary terms, when section 4 is met: typically by using the library as a replaceable shared library, giving notice of its use, and including the licence.
proprietary code in a project licensed under LGPL-3.0: See Proprietary source-disclosure conditions.

Attribution

LGPL-3.0: Provide source of the library and of modifications to it when distributing.
LGPL-3.0: Give prominent notice that the library is used and that it is covered by the LGPL.
LGPL-3.0: Accompany the Combined Work with copies of the GPL and LGPL.
LGPL-3.0: Provide a way to relink or use a shared library so users can run a modified library version (section 4(d)).
LGPL-3.0: Provide Installation Information where required for User Products.

LGPL-3.0 code in proprietary software: LGPL-3.0 requires the copyright and licence notices to be kept with copies you distribute.
proprietary code in a project licensed under LGPL-3.0: Proprietary attribution requirements apply on distribution.

Patent Considerations

Express patent licence: LGPL-3.0: yes; Proprietary: depends on the licence agreement.
Patent termination clause: LGPL-3.0: yes; Proprietary: depends on the licence agreement.

LGPL-3.0 code in proprietary software: LGPL-3.0 includes an express patent licence from contributors. That patent licence terminates for anyone who initiates patent litigation alleging that the work infringes a patent.
proprietary code in a project licensed under LGPL-3.0: Patent terms are unknown.

Common Scenarios

Scenario	LGPL-3.0 code in proprietary software	proprietary code in a project licensed under LGPL-3.0
Use as a dependency / library	Compatible With Conditions	Manual Review Required
Copy source code into the project	Potential Conflict	Manual Review Required
Modify the component	Compatible With Conditions	Manual Review Required
SaaS / network service (not distributed)	Generally Compatible	Manual Review Required
Internal / private use only	Generally Compatible	Manual Review Required
Resell the software	Compatible With Conditions	Manual Review Required
White-label / rebrand	Compatible With Conditions	Manual Review Required

FAQ

Can I use LGPL-3.0 code in proprietary software?

Using LGPL-3.0-licensed code in a proprietary project is generally possible if the listed conditions are met. An application that uses an LGPL-3.0 library may be distributed under its own terms, including proprietary terms, when section 4 is met: typically by using the library as a replaceable shared library, giving notice of its use, and including the licence.

Can I use proprietary code in a project licensed under LGPL-3.0?

Using Proprietary-licensed code in a project under LGPL-3.0 requires review of the actual licence terms. The component is under proprietary terms. Whether it may be used, modified, redistributed, resold or white-labelled depends entirely on the specific licence agreement.

Do I have to publish my source code when I use LGPL-3.0 code?

Can I use LGPL-3.0 code in a closed-source SaaS?

Using LGPL-3.0-licensed code in a proprietary project is generally compatible in this scenario. LGPL-3.0 copyleft conditions are triggered by distribution; this scenario does not include distribution.

Try the Interactive Checker

Change the scenario, say whether the code is modified, distributed or offered as SaaS, and see every rule that applies.

Check LGPL-3.0 in a Proprietary project Check Proprietary in a LGPL-3.0 project

Related Comparisons

Authoritative Sources

This tool provides general software licensing information and is not legal advice. License obligations may depend on how software components are combined, modified, distributed and used. For high-risk results, review the actual license text before relying on this result.