Donkey Konga 3 consisted mostly of music from animes that were really popular there so they would have to revamp the entire soundtrack would it get released outside of Japan, kind of defeating the point. That, or it was just more popular there than it was elsewhere. (It should be interesting to note it also had covers of the Japanese intro and ending of the DKC cartoon in its soundtrack.)
For as far as I know it's not available for the GameCube outside of the Japanese one. You could always take a look on eBay and get a freeloader along with the Japanese edition of the game, though. I'm planning to do so, some day.
Whoa, this topic is a year old? Meh! I sure took my time typing, so I'm still posting it!