Simon Janes If I ever do find a need to self-host GitLab, there's a Slack alternative you can also self-host, gitlab.com/gitlab-... for mattermost.org

Mark Dain I never understood why everyone likes Slack. Doesn't it do the same job as HipChat?

Simon Janes You can at least install a HipChat for your own server, but is closed-source as best as I can tell. You can't do a private server instance with Slack.

Mark Dain Slack is also closed source and as you pointed out, you can't self-host which is a no-go for businesses.