Comment by kelnos

> That has nothing to do with the software being open source or not, it's a question of whether you have a robust archival system in place.

With Slack, your only option is to pay per user in order to have access to older messages, which is almost certainly going to be cost-prohibitive for most projects. I don't have a source for this, but I believe using a bot that automatically archives conversations elsewhere is against Slack's free-tier ToS.

I agree that this doesn't inherently have anything to do with closed vs. open source, but these sorts of shenanigans just aren't possible if you're self-hosting an open source discussion platform.