There are two ways to see: First click the credits button in the Planeshift main menu, and you should see a list of composers (im assuming, im too lazy to try this again).
Secondly, If you convert the Planeshift music to .mp3 files, then the composer information is converted as well, and you should be able to view it if you use iTunes or WMP 10. (You definatly can for iTunes, not sure about WMP).
As for the music itself, it is bloody good, I\'ve (like alot of other people) had sound turned off for ages due to the errors it gives, which is a shame because the music really is top class stuff. If you want to listen to the music seperatly from Planeshift, you need to either get a .ogg plugin for your media player, or go to
http://www.4musics.com/ogg-mp3-converter.htm and download the .ogg to .mp3 converter, and then convert the files. They are in Planeshift / Art / Music.