I suppose if zluda interpreting native cuda code on other IHV platforms is "illegal", whereas HIP can legally be used to translate CUDA to ROCm at runtime, I would equate WINE to HIP, as it translates Windows API calls to POSIX for linux and Unix systems.

I'm not sure Microsoft have a leg to stand on with a move like this given their legal troubles in the past around becoming a monopoly. Maybe they don't see as much threat given the low share of linux and unix (including mac) desktops

There's still a bit of friction around actually leveraging WINE on non-Windows systems, with Proton being a relatively recent outlier as it offers you a mostly plug and play experience via steam, lutris and others.

For nvidia, zluda can allow other IHVs with significantly cheaper DC solutions to undercut them with no friction whatsoever.