It looks like, as long as the app can use the API, it'll stay updated for iOS 11 (the author states he updated it as soon as he could), and so it'll likely function for a while.
Yeah, I'm using it on iOS 11 and it works great (although I don't love the new native video UI Apple is going with) - my concern is that YT will be dicks and kill access through the API. I sure hope not.
