Being open-source isn't exactly a major virtue here as DLSS can be freely implemented even in paid mods (see: the Starfield upscaler mentioned earlier in the thread: the author asks $5 on patreon for access for the version with DLSS frame generation support, and even implemented a DRM which requires you to validate your patreon account as a paying customer to avoid mod piracy - that's the depths of insanity we've reached), it just can't be built from source.
And again, it's all about customer agency: sure, FSR works on Nvidia, but it doesn't have the best results, and even if it did, who's AMD to decide for you what technology you should be using? It's this very reasoning that drove me away from the PS3 when I built my first PC in 2008, I don't want billionaire megacorporations deciding how do I get to experience my gaming or use my hardware.