Basically playing the music as taken less-than-willingly from the game itself. I can't imagine it would be too hard to find the music around somewhere. Wouldn't it be sweet if he did release an OST, though?
Of course, I do have a suspicion that that idea might run into the typical auteur objection, such as: That's not how the music is meant to be experienced. I certainly hope that's not the case, but if not, one would wonder why he hasn't released the tracks already. Seems like a very obvious move, after all.