How dare you choose not to put yourself in legal jeopardy for the sake of random people on the internet!
Please feel free to ignore everyone here. You made a Cool Thing, it didn't work out, whatever. You'll probably make more Cool Things in the future and I hope they'll stick!
I don't think we need people who can actually create things to waste time in bureaucratic legal battles. Go make other things; there's obviously no way to make Slack better.