Well, you could always implement a fallback for unsupported devices and advertise for better performance on supported devices. Implementation will usually be "sponsored" by the one providing the technology. If the feature then gets adopted enough others will have to come up with something similar or support it native, too. This happens all the time with GPU and CPU vendors, both in gaming and industry.
Maybe, but I got the sense from the article that what NVIDIA has patented are the semantics of the API itself (i.e. the types of messages sent between the CPU and GPU.) A polyfill for the API might still be infringing, given that it would need to expose the same datatypes on the CPU side.
And even if it wasn’t, the path-shader semantics are so different from those of regular 2D UI frameworks, that a 2D UI framework implemented to use path-shading, that falls back to using the polyfill, might be much worse performing than one implemented using regular CPU-side 2D plotting. It would very likely also suffer from issues like flicker, judder, etc, which are much worse/more noticable than just “increased CPU usage”.
