[avar]

I'm no fan of Slack, but it has IRC and XMPP gateways. You can trivially set up an IRC bot that logs your channels & conversations, I connect to Slack via irssi & use its standard logging facility.

So you're no more likely to lose your logs via Slack than via IRC or XMPP if you set things up correctly.

[unimpressive]

So what you're saying is, Slack works great as long as you're willing to perform some 'uber geekery'? ;)

[avar]

How do you think open source projects have preserved message history on the existing open source alternatives discussed in this thread (IRC & Jabber)? You set up & maintain your own logging bots.

[aeze]

I don't know if I'd consider that 'uber geekery'... it's just setting up an IRC client - they provide instructions on the slack website.