Mergekit is relicensed under LGPL v3

Arcee's Mergekit, the toolkit used to combine, or 'merge,' the weights of multiple language models into one, had been released under a custom Business Source License. Arcee's blog post explaining the change says that license was adopted to balance community access against the risk of a large competitor commercializing the project without contributing back.

Arcee says that custom license created legal gray areas that slowed adoption even when the actual answer for a given use case was permissive: teams had to route it through legal review, and the resulting hesitation discouraged startups and contributors from building on it. It also left Mergekit out of step with the rest of Arcee's stack, since its own models ship under the permissive Apache 2.0 license.

As of October 31, 2025, Mergekit is licensed under the GNU Lesser General Public License version 3, a standard open-source license that permits linking it into proprietary software. Arcee frames the change as removing that friction rather than altering how the tool works.