For a short time, "game music" referred to bedroom producers riding a wave of Commodore 64 computer nostalgia and writing retro-futuristic music pushing its crude sound chip to its limits.
Délire, aka New-Zealander Julian Oliver, has developed a true form of game music -- not a video game soundtrack, but game-based audio synthesis, electronic music that you "play" through a computer game instead of using a keyboard, a sampler or audio synthesis software like Max/MSP. Imagine a gaming environment like Quake or Unreal in which each movement of your first-person character triggers a sound, or the modification of a variable of a given sound.
Diaspora appears to have been produced just like that, although no details are given about the 11 tracks on the audio portion of the CD. But an enhanced portion contains two Quicktime movies of the "game" in progress and the mechanics of it are fascinating.