That's interesting. I thought the point was that it needed to be in-kernel for performance reasons; if it works in userspace why did linux not do that?

Ideally it does need to be in-kernel for performance reasons. But that's not possible on macOS, so it's better to have it in userspace than not at all.

But does anyone care about MacOS? ;)

I mean, I know Mac has had some great games (eg. I spent so much time on school Macs playing that Bolo tank game) ... but they have probably <1% of the number of games Windows has. I'd expect a simiilar percentage of devs to be interested in Mace (or whatever you call Mac Wine).

Not sure what you mean. The number of Mac games isn't relevant to a subthread about a project to increase performance when Windows games on Mac.