Mattermost say they will not clarify what license the project is under

Mattermost is dead. Just forget about it.

UPDATE Feb 2, 2026: To be specific, our license is using standard open source licenses, a reciprocal AGPL license and a permissive Apache v2 license for other areas. Both are widely used open source licenses and have multiple interpretations of how they apply, as showcased in this thread.

When we say we don’t “offer the clarity the community would like to see”, that refers specifically to the many statements in this thread where different contributors are confused by other people’s comments and statements.

For LICENCE.txt itself, anyone can read the history file and see we haven’t materially changed it since the start of the project.

If you’re modifying the core source code under the reciprocal license you share those changes back to the open source community. If you’d like to modify the open source code base without sharing back to the community, you can request a commercial license for the code under commercial terms.

Sounds like you are allowed to do actual open source on the project, but mattermost might sell your work to others who don’t want to share their work back with the community. Which is a violation of the open source licenses, specifically the AGPL (I’m not certain on Apache?).

Sounds like a dick move, regardless of license violations.

wtf is mattermost again?

This would be easily solved by just forking the project. If they complain that a fork infringes their work then that is the clarification.

Cool. Cool cool cool.

Mattermost is indeed, a dick. They try to leech off of contributors like many of corporate focused open source products do.