I have no idea if Slack could actually win a case, but in the US (where both companies appear to be headquartered) they do have some rights to look and feel as part of trademark law.
Interesting. There's potential for that as a basis for a civil suit, but i really doubt that the open source alternative could really be argued as trying to misrepresent or cause confusion as to the origin of the product. It'd be a hard case.
I have no idea if Slack could actually win a case, but in the US (where both companies appear to be headquartered) they do have some rights to look and feel as part of trademark law.