Docs / Licensing and legality
Licensing and legality
Why Mattermore is legal: it modifies AGPL code only, never the Source Available Licence, and documents a switch Mattermost ships itself.
The short version
Mattermore modifies AGPL-3.0 code only. It does not modify or redistribute anything covered by the Mattermost Source Available Licence. That is the central legal fact of this project, and everything below is detail supporting it.
Mattermore itself is released under AGPL-3.0, the same licence as the upstream code it builds on.
How upstream Calls is licensed
mattermost-plugin-calls is dual licensed. LICENSE.txt in the upstream
repository grants:
- AGPL-3.0 for the source code.
- MIT for compiled versions produced by Mattermost, Inc.
- Apache-2.0 for the contents of
webapp/i18n/.
The plugin also carries a second file, LICENSE.enterprise, which is the
Mattermost Source Available Licence. It covers server/enterprise/. That
licence permits modification for development and testing only, and requires an
E20 subscription for production use.
Those two licences cover different directories. Keeping the line between them clean is what makes a fork like this defensible.
What Mattermore actually changes
Group calls need no patch at all.
The licence check for group calls lives in GroupCallsAllowed() in
server/enterprise/license.go, and it already reads an environment variable:
os.Getenv("MM_CALLS_GROUP_CALLS_ALLOWED") == "true"Upstream ships that switch themselves, in every released version. Mattermore documents it rather than patching around it, which is why nothing under the Source Available Licence is touched. See the configuration guide for how to set it.
Everything Mattermore does change sits in AGPL-3.0 code, and those changes are published under AGPL-3.0 in turn.
Precedent
Framasoft’s Mostlymatter has forked the Mattermost server the same way since
May 2024, patching only AGPL code in server/channels/app/limits.go.
It is a long running, publicly maintained example of the same reading of the same licences.
Trademark
“Mattermost” is a trademark of Mattermost, Inc.
- Mattermore uses the name only to describe what it is compatible with, which is nominative fair use.
- Mattermore does not use Mattermost’s logo, wordmark or brand colours.
- Mattermore is not affiliated with, endorsed by, or supported by Mattermost, Inc.
Note that the plugin id stays com.mattermost.calls, because the server
expects it. That is a technical requirement for the plugin to load, not a claim
of origin.
Be fair to Mattermost
Mattermost open-sourced this code, and they added the environment variable themselves. Group calls on a self-hosted server are possible because they made that choice.
If your organisation can afford Professional, buy it. That revenue funds the upstream work this fork depends on. Mattermore exists for the people who cannot justify a per-user subscription for a handful of audio calls, not as an argument against paying.
Not legal advice
This page explains the reasoning behind the project. It is not legal advice. If the licensing of your deployment matters to your organisation, have a lawyer read the licences and decide for you.
Once you are satisfied, the install guide is the next step, and troubleshooting covers what to do when something does not work.