Sinister is still around, albeit a lil less visible. They don't make the Gruitr any more but used one's pop up on Ebay and Busted Spoke from time to time. They do make a new Shenanigan (2 models) that is pretty damn sweet. Yea, the Sinister message board has been dead for a long time, too bad.
You can contact Frank D. via email..........his email address is on the Diesel Bikes website.