[swiley]

So if they accept contributions from the community does the copyright on those get reassigned to mattermost?

[jsty]

No, it's a "grant to Mattermost and to recipients of software distributed by Mattermost a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute your contributions and such derivative works."

https://www.mattermost.org/mattermost-contributor-agreement/

https://spinpunch.wufoo.com/forms/r3z8zqm0ew6pcc

[driverdan]

No, that's not how copyright works.

[johncolanduoni]

There are software projects that use/require copyright assignment (notably many GNU projects require assignment to the FSF).

[bildung]

Yes but in these situation the copyright assignment is a separate contract underwritten by the person committing. What (I think) driverdan means is that an OSS licence legally cannot substitute this separate contract - one cannot automatically assign one's own copyright to another entity by following an OSS licence.