[bfkwlfkjf]

What's mattermost? People in the GitHub comments say "I just need messages" but there's lots of self hosted messaging apps/servers, no? XMPP comes to mind immediately.

[firesteelrain]

It’s an IRC-like, group chat for Corporate that works in airgap. When HipChat was obsoleted, then Mattermost took over.

[figmert]

It's an open source alternative to Slack

[hk__2]

Well, it was this at the beginning. Now it’s an open-core competitor to Slack, with higher pricing(!) but you can use the free version that has fewer features.

[loeg]

My employer migrated to it from IRC, for example.