Seems like the sort of thing that would prompt a legal smiting from Nintendo, along with others.
On what grounds? Hard to patent, trademark or copyright an arrangement of, usually off the shelf, chips. Interoperability is also a fairly persuasive argument to some of those.
If it came with non free/PD ROMs, BIOS/firmware dumps (many such things have free replacements these days) or maybe if they could demonstrate it was made with knowledge not available to them (usual being when a bug from a manual* is replicated in emulator despite nobody doing a hardware analysis ever coming to that conclusion) then that would be one thing but you would have thought "they" would have done something long before then.
*I did read an interview with one of the dolphin writers/project management types a while back. He said they had to occasionally ban with extreme prejudice the occasional new coder saying they had access to the manuals and were willing to help.
Anyway never been a fan of these all in one emulator pack things (theoretically they should be good, the reality seldom ends up there), and the few interactions I have had with the retroarch folks has left a bad taste in my mouth, and also have no fondness for Steam but don't see this as a bad thing.