Sure, you can use the music under both the GPL and Creative Commons NonCommercial ShareAlike (allowing you to modify, display, and perform the music wherever you like as long as you don't make money off it, and license any derivatives under CC-NC-SA as well if you plan to release them.)
There might be some transcoding loss from going to OGG (a lossy format) to MP3 (another lossy format), but you probably won't notice this much unless you are a major audiophile.
If you are concerned, there may be some MP3 masters around somewhere... I believe that there are also masters in a lossless format somewhere (wav or aiff) but you'd probably have to ask for them.
The third option is to buy the
Vega Strike CD, which comes with CD-quality tracks (but it might be a bit outdated, I'm not sure.)