The issue is one of licensing, not technology. There’s all kinds of patents in the space, and using free codecs could still infringe them. DirectX doesn’t have the same patent protection. I believe in theory you could make a fully open source Linux native version of DirectX.

For more info from someone who knows more than me, see here.

Well, sometimes Windows games depend on propietary codecs, and until Valve can get the devs to make adjustments so the codecs aren’t needed, the games aren’t going to work properly in regular Proton.

If GE received a Cease and Desist, that would be frustrating, but linux gaming would go on. If Proton got a Cease and Desist, that could be catastrophic to linux gaming. Valve could even theoretically get banned from working on linux gaming (like the Yuzu devs got banned from working on emulation). It’s just not worth the risk for compatibility/performance for a smaller proportion of games.

Nvidia already opened their driver, at least to the same extent as AMD, which is why NVK is able to exist.

I’m not sure about the latter

I believe it was Xwayland 24.1 that recently released that brought explicit sync support, so you’ll need that.

Seems like a good redesign.