What does "fork of wine" mean concretely? As in, what does Proton give me that Wine doesn't? The way you make it sound is that it's a "Wine distribution"; is that correct? Or does it do more?
It's not really a fork, more like a distribution as you might be familiar with it, or built on top of Wine. Without Wine, there probably wouldn't have been any Proton.
I think parent mean "fork" in the strict sense that there are two source codes "versions" of Wine: upstream, which is the official wine you get when doing `apt-get install wine`, `pacman -Ss wine` or whatever. Then there is Valves own clone of that same codebase, but with additional patches on top of it. Many changes are game specific, at least in the beginning, but many are also generalized and eventually "upstreamed" to the official Wine repository.
So in a way, they maintain their own fork with their own set of patches, and some of those patches makes their way to the "original" Wine while some don't.
