Well, on-the-fly-improv type soloing isn't my strong point with the guitar (I've still been working on it, although I'm slowly getting better), and it didn't help that I didn't sleep well last night, but here is one attempt:
http://www.destructavator.com/public/UFO_AirC_3_7.oggOr, if that doesn't sound as good as you hoped, I slightly touched up the last version:
http://www.destructavator.com/public/UFO_AirC_3_7x.oggI'd say you could go ahead and commit whichever one of these you think is better, unless you'd rather wait until I have time to try a better solo at the end, which could take a while through the next week or so at least, partly because I have other things to attend to and partly because I've worked with this tune so much I need a serious break from it. (This happens in songwriting and composition, making a great song but being sick of it at the end because of hearing the same parts over and over again.)
Oh, and I almost forgot, it can go under the same CC license as the other tracks, as long as that license will still work.
I've done a little research on compatibility between Creative Commons and GPL, and I believe GPL version 2 is indeed compatible with the most recent CC attribution-share-alike unported (meaning non-nation specific) as I've seen other free games use this combination for code and media content.
GPL is really meant for programming code, while CC is really better for media and content, from what I've heard. On the other hand, if you guys want the whole thing GPL, I'm guessing I'd have to upload the "source" which in this case would be the DAW multitrack audio files, which I'm willing to do, but would be a rather large zipped file (The MIDI is tiny but the .WAV files, 24-bit, are quite large).
If anyone here is an expert in these license matters, feel free to correct me.
Regardless, I think this track (either version) should work nicely for the game.
-Dave