it’s not a problem of licensing per se, Spotify as a platform doesn’t work like that.
The correct question is:
“Does Spotify offer a public API/plugin that can be used?”
The answer is still no probably.
I would think that once Spotify see the potential of that, and there is, win-win, make a plugin/API et voila, Spotify becomes the de-facto standard in videogame music, they are missing a trick there!
Some expansion of their API here would be a killer: