I was looking at using Slack but wanted an OSS version - can anyone recommend one? I like that OTR is going to be an option with chatgrape, my team uses Adium w

I was looking at using Slack but wanted an OSS version - can anyone recommend one? I like that OTR is going to be an option with chatgrape, my team uses Adium with Jabber, but it could be a lot better.