Kam's past was explained in the unreleased novel Lightsider by Tom Veitch. It appears either Kevin J Anderson read a draft of the novel or was told about the plot by Veitch himself. Either way, Anderson made mention of the story in his Jedi Academy Trilogy and we're told that's how Luke brought him away from the Dark Side by beating Solusar in a game of Lightsider.
Shown in the Dark Empire II comic, readers were supposed to have already read the unreleased novel which took place between the Dark Empire I and II so the explanation of what Kam is doing with Luke in the beginning of the comic is never clearly explained to the reader.
I for one was very confused after read Dark Empire II because I felt I'd missed something. Much later when I discovered the story was never released, I moved on from it and accepted Anderson's brief mention of the event was the best we'd get.
All that's mentioned afterwards is that Kam excelled in his studies and became one of Luke's best students at the academy. Though mentioned in several stories from New Jedi Order and on, Kam never got a chance to shine in his own plot line which I would've loved to have seen.
Though mentioned in the Jedi Academy Trilogy, his role is very minor, hence why he finds himself among the ranks of Luke's Forgotten class!