I've installed GrayJay to try and replace ReVanced with something that doesn't show me video recommendations and doesn't have ads, and I have some doubts about Louis' claims that GrayJay does not use YouTube API's. To import my YouTube subscriptions, I had to log into my YouTube account via GrayJay, and it pulled my subscriptions that way. Plus, it has optional settings for enabling authenticated client connections.
All of this will inherently use YouTube's API's, and I'm not talking about your usual yt-dlp scraping. So I believe that YouTube's complaints are legitimate as FUTO has designed GrayJay in a way where it does in fact interface with their API's to pull your subscriptions and playlists. If it were done the way NewPipe does it, which is way more cumbersome but bypasses any sort of API activity, where you have to use Google Takeout to pull .csv's of your subscriptions and playlists, YouTube would have less ground to stand on to send legal letters like that. But then of course, the app wouldn't be as nearly as attractive as it is right now, and in the end, YouTube doesn't give a shit, they'll make up any excuse to shut the project down as they fight against all forms of alternative YouTube access that doesn't generate them profit.
As for the people yapping about how GrayJay is not open source because of their FUTO Temporary License that makes the project source available at best, well, here's the thing. It has to make money and protect itself to exist. It's a project that goes against corporate interests, no corporation will be willing to fund it. They cannot operate as yet another FOSS kibbutz like NewPipe if they want to get somewhere. NewPipe is a FOSS kibbutz and it has constant issues with playing YouTube videos, it's interface is clunky and it's overall a miserable experience if you want to use it for video viewing. GrayJay is more mature and feels a lot like the official YouTube app. Not only that, it aims to be a much more robust app in it's functionality. It's a massive project that needs funding and organization to thrive, and it can't just give it's code away under GNU GPL. And assuming that the license has "Temporary" in it's name, it is in fact a temporary protection as the project gets developed. Though only time will tell where that'll go.
To be honest, I'm impressed that FUTO operates on this honor system, where GrayJay is perfectly fine to use without a license, but they do ask you politely to support the project financially, because they need it to keep developing it.

At least, that's how I understand it. The license is optional, it's meant to act as a token of support for the project so it can be developed further. I couldn't find any information on their websites about any sort of limitations on the app's functionality without a license, nor did I experience any, so I assume it really is how it works. You can be a nigger faggot and freeload like me, or you can be a white man and pay them for a license. All it will do is that it will hide the "Buy" menu, but it's like Louis has said repeatedly with his copy of SuSE Linux. Even though it's free, if you found value in it, you should financially support the creators.
I also tried the other FUTO project, the FUTO Voice Input. It's good, but only when it comes to English. It can perfectly recognize my wonky accent at the standard settings, but their Polish model still has a long way to go, as it was only somewhat acceptable when I used the slow large model. The regular one made a lot of weird mistakes, but hopefully they'll manage to improve it in the future. It would also be really cool if it could act as a private replacement for "OK Google" that can interface with other apps that utilize Google's Home Assistant functionality. I'd like to use voice commands to for example call someone while I'm driving or change the song that I'm listening to, but I don't want Google to constantly listen to what I say just to give me that functionality.