This may help.
Usually, canon in game is any dialogue or item or quest that MUST be said, accomplished or used for the main story to be accomplished. For instance, rescuing Zaalbar, storming the Velkar Base, and winning race before the swoop explodes and kills you are cannon events. Details, however are vague, very vague.
You will notice that many times if you choose a different dialogue option, you will still get the same response, so even if what you say is not canonical per se, the other chaps very well may be. The essential 'bone' of the dialogue is also very important to use.
To anyone writing a Star Wars fanfiction, I recommend reading at least summaries of all the Tales of the Jedi comics, the Star Wars Tales comics Unseen, Unheard and Shadows and Light. Crucial to such research is the reading of the actual KotOr Dark Horse comics. Since they have appearances from Carth, Mission, Griff, Gadon, Brejik, Cassus Fett, Mandalore the Ultimate, Sual Kareth, and Jedi Revan and Malak. Now don't quote me on this but I think Krynda Draay is Kreia, but that's merely speculation.
The second game does confirm this, if you specify lightside male Revan. Carth and Bastila survive. Bastila and Revan had a relationship. Though it never does say if Revan killed Juhani or not.
If your friend is writing a fan novel, I recommend sticking to the essential skeleton of the Light Side Male story line while using discretion to figure out what dialogue, action, ect. would most enhance the meat of the story. Such as, making it so the planets are in this order Dantooine, Kashyyk, Manaan, Tatooine, Korriban. Since we all know what happens when you find starmap four and go to another planet, you could have Revan wrestling with the events that transpired onboard the Leviathan while in the academy on Korriban to heighten the tension; make the reader wonder, 'is the hero finally going to crack?' Since all that has been stated is that Revan finished the quest a good guy and stayed predominantly good while doing it, we can write between the lines as it were. Or, you could explain how on earth Bastila was smuggled through Taris after the swoop race without being captured.
Again, just thoughts.
"Raking is easy, but all you get is leaves.
Digging is hard, but you may find gold.”
“Like a gold ring in a pig's snout is a beautiful woman who shows no discretion.”
"Get thee gone from my gate, thou jail-crow of Mandos!"
-Feanor to Morgoth