https://www.atlassian.com/licensing/purchase-licensing https://www.atlassian.com/licensing/purchase-licensing Atlassian probably fits the bill more and has pro

https://www.atlassian.com/licensing/purchase-licensing https://www.atlassian.com/licensing/purchase-licensing Atlassian probably fits the bill more and has proven revenue on it, while Slack is more... "SaaS" in my mind, and really hasn't proven long term revenue traction yet, though it is certainly looking good for them.