You're right, they can't prevent that, but they can change their APIs in breaking ways enough to make librespot unreliable, to the point it's just not worth it.

I assume that for a long time, Spotify was content to ignore projects like librespot... they didn't help those projects, but didn't harm them either, and generally to keep things stable enough that a project based on librespot basically stayed working, which is why you saw so many OSS tools that used it behind the scenes. It does seem like that balance shifted over the last year, and now librespot is constantly breaking in new and mysterious ways. Some accounts work, others don't. Some tracks play, others don't. The devs did a great job fixing that stuff, but it's a game of whack-a-mole, and Spotify seems to have really upped the frequency of how often they break things. And that's for the lossy decoding, which is functionality that used to be pretty stable. Spotify reached out and (I assume) made some threats that explicitly shut down their work around lossless audio [1].

FYI -- I'm not associated with the librespot project, but I was actively working on a project that relied on it. Eventually I gave up in favor of self hosting, because I want my music to not break all the time. Shame, because I used to like Spotify a lot and now I'm actively looking to move away from it. That's one premium family plan subscription they're gonna lose! I'm sure they'll feel the sting.

[1] https://github.com/librespot-org/librespot/issues/1583#issue...