iTunes does not sell karaoke
iTunes (and Amazon too) makes the claim that they sell karaoke. Unfortunately this is a bald faced lie. Karaoke, in just about anyone's book, means there are synchronized video lyrics that play with the song. iTunes does NOT sell karaoke, instead it sells "instrumentals", that is, a version of the song with no lead vocals. This does NOT include any video portion.
So if you bought some so-called "karaoke" from iTunes, you have been duped, and ripped off. Sorry about that. Yes, you can transfer said songs into kJams, but you'll still ONLY get the audio track (video screen will remain black).
You can, if you're intrepid, add the synced lyrics yourself using Producer.
What you really want to do is buy *real* karaoke music using the kJams Music Store.