Good points. Also it's a bit of a stretch to say the different parties are using it for free anyway, because professionally maintaining infrastructure in a way where even a bit of resilience is expected is not cheap. The budget for running these self-hosted platforms can easily be eaten by one person's salary + infrastructure costs. It in many cases would probably be cheaper to just pay for Slack, but because of some requirements they rather pick one of the open source ones and do what they can within the allocated budgets. I doubt there's any malicious intent in these situations, or any wish to just be freeloading, but something a bit more complex.

Ofc would be nice if money was flowing the right direction.