It opened a whole bevvy of open and useful Spotify clients that worked amazingly and some that still do to this day. Mopidy, as well as a handful of amazing MPD-speaking daemons got me through college. The only conceit was that it required a premium account and yielding a third party client your authentication data. They had some issues with Facebook authentication as it was OIDC, but setting a user name and password on your account was a simple solution.

The Spotify team has killed libspotify in preference for a Javascript browser or Mobile Device library (ios/ObjC or Android /kotlin) that uses the browser to authenticate over openID. It can only be a connect target, not query the full api, and depends heavily on the browser or native api to play the media.