[nerdponx]

Also Mopidy, which lets you use Spotify from any MPD client.

I suspect that secretly there are some people at Spotify who are sympathetic to open source and/or use Linux, and have convinced the business people and bean counters that not being openly hostile to free software is good business.

I have mixed feeling about Spotify in general, but it's still not as "closed" of a platform as it could be, and I'm at least a little bit happy about that.