this might help
http://en.wikipedia.org/wiki/Creative_Commons_License
and found this at the bottom... labelled free music...
http://en.wikipedia.org/wiki/Free_Music
if you go down a little on that page you will see this list...
Quote: "
Record labels and websites distributing free music
Audition Records free and non-free CC licenses[15]
Dogmazic — free and non-free CC licenses, GNU GPL[16]
Free Music Archive
Jamendo (free and non-free CC licenses, Free Art License)
LOCA Records[17][18]
Magnatune
Opsound
Sean Terrington Wright (free and CC licenses, Free Art License)
Starfrosch
"
they are all linked on the second link above
GNU GPL might be the licence you are looking for but do some searching to figure out which you are looking for...
I think I will add those links to my blog too >.< or maybe just my wiki...
this one was interesting
http://en.wikipedia.org/wiki/Jamendo
website
http://www.jamendo.com/
I was just listening to this one...
QUALITY!
but looks like the listening is free... beut I noticed something weird...
home page says
Quote: "
Listeners
•336,561 free music tracks
•Stream and download for free
•Unlimited and legal sharing
Listeners
•336,561 free music tracks
•Stream and download for free
•Unlimited and legal sharing
"
and also
Quote: "
Professionals
Royalty free music licenses
CatalogRatesTestimonials
Royalty free background music
Free trialRatesTestimonials"
so I guess you still need to fish through the rest of those links and see if you find some royalty free, free tracks that you can use... but Jamendo seems like it will need payment for royalty free licences to support the artists

you never know maybe theres a free one so just sieve through the lot...
hope this helped... and sadly I think I will not link to this stuff... as I already am in talks with a musician to produce music for my upcoming titles so...
I also think I will ask some of the wonderful composers on here to help with some of my projects both free projects and paid projects... meaning projects that I sell onto customers... so i also pay the musicians
anyway yeah hope this helped somewhat...
OH and thinking again... that Jamendo and others maybe as it says free distribution is free and legal but I guess your project might fall into that category... maybe just contact individual artists and say you will link back to their store or something... and of course do that anyay!