Grant Kirkhope was recently interviewed by Nintendo Nation about a variety of subjects.  Fortunately for all of us, the DK Rap was brought up.  It seems the idea came from George Andreas at Rare, with several Rare staff members contributing their voices and Kirkhope recording it all.  Kirkhope and the rest thought it was hilarious, but weren't expecting gamers to take it as "a serious attempt at writing some kind of really great rap song."  Kirkhope also mentions seeing a clip of a "a real credible [Japanese] rapper" doing a serious version of the song.

We can only hope that a clip of the serious, hard core DK Rap surfaces soon.

Source: Nintendo Nation