Yep, that be it. On their forum they also talk about winding your own transformer since it does not exist on the market. I was looking on eBay for the Geiger tube and they don't seem to come cheap. In the long run it is probably less costly to buy their kit then to scratch your own.
BTW: Your link had double url tags so it didn't work http://radioactiveathome.org/images/prototyp8.png