Dual Licensing (Open Source + Commercial)

What is dual licensing?

Dual licensing is a software distribution strategy under which the same codebase is offered under two distinct licences: typically a copyleft open-source licence (e.g., GPL, AGPL) for non-commercial or community use, and a separate commercial licence for proprietary or enterprise use. Dual licensing lets vendors monetise software while preserving open-source community engagement; it requires the vendor to hold copyright (or have CLA-equivalent rights) to all contributions so it can grant both licences.

Mechanics of dual licensing

• Copyright concentration: vendor must own (or have broad CLA-assignment of) all contributions to grant proprietary licences.
• Open-source side: typically strong copyleft (GPL, AGPL) so that proprietary users cannot avoid the commercial licence by using the OSS terms in closed-source products.
• Commercial side: bespoke EULA — no copyleft obligations, optional support/SLA, indemnity, professional services.
• Trademark separation: distinct trademark policy reserves brand rights for paid version.

Famous dual-licensing examples

• MySQL (Oracle, ex-Sun/MySQL AB): GPL v2 + commercial — the canonical dual-licensing case.
• Qt (Qt Group): LGPL + commercial for proprietary integration.
• MongoDB (until SSPL pivot 2018): AGPL + commercial; later abandoned dual-licence for Server Side Public License.
• Elastic (until license change 2021): AGPL + commercial; later moved to Elastic License + SSPL.
• Sentry, Plausible, Cal.com: modern AGPL + commercial dual-licence open-core companies.