Stargate's cannon policy is a mess, as of now, we don't know and unless it directly contradicts anything in the show we may not know for quite a while--18.104.22.168 18:40, August 14, 2010 (UTC)
To put shortly, novels published by Fandemonium are currently classed as cannon by MGM. Here is the long explanation, which was explained by Jo Graham...
First Fandemonium submit an outline of a story, with all major characters and plot in it, following the guidelines that they are given about content. That outline was modified by MGM. We made changes in response to their feedback, and then resubmitted the entire outline. Then for EACH book they submit a 5,000 word synopsis detailing more closely the entire plot. Each synopsis is then edited by MGM and returned. Fandemonium resubmit until it meets their approval.
When each book is finished it goes to our editor at Fandemonium, who requires changes which they make. Then the manuscript goes to MGM, where it typically stays 3-6 months for detailed LINE BY LINE WORD BY WORD edits. Usually there are 200-300 individual changes suggested by MGM. Fandemonium make changes and rewrite. Then the manuscript is resubmitted to MGM where it once again has a LINE BY LINE WORD BY WORD edit. Any remaining changes are made.
There is not one single WORD that has not been approved by MGM three separate times. Everything, every last comma, is reviewed exhaustively to meet their requirements.
Of course, as the owners of the franchise, MGM can change their minds about canon at any point in the future, retcon or rewrite as they wish, just as in a future show they can choose to retcon or disregard anything that's been previously filmed. But yes, it is canon. Every single word is approved by MGM, the owner of the franchise.