Slack is awesome. It's way better than IRC in many ways. But I agree with the OP. Please don't use it for FOSS projects, use it for your company or other privat

Slack is awesome. It's way better than IRC in many ways. But I agree with the OP. Please don't use it for FOSS projects, use it for your company or other private use cases. But FOSS projects an communities require open tools. Slack won't save your history unless you pay for the service. The pricing is per user which makes it very bad for a FOSS community.