I believe insanejournal runs on the same engine as livejournal; at least, it looks like it outputs html the same way. if that's so, and if they have friending just like LJ, then there's no reason I couldn't plug into insanejournal as well as any other lj-type journals (such as greatestjournal).

However, I will be running the pilot program off of LJ, and hammering out the kinks there, since LJ has the most users. Other journals would come after the primary functionality had been worked out.