Hey, Wiimm.
The Custom Mario Kart community seems rather active (fortunately), judging from the recent releases. However, the forums themselves, don't seem very frequented. I just signed up there and later realized most posts were really old. I think part of the reason might be that the forums are not linked from the wiki. I found it by searching google.
Is pherhaps that forum not associated with your wiki?
Do you have a forum where you discuss projects and events?
I'm very interested about what you guys are doing and would like to keep more abreast of the projects, etc.