It's mad! As far as I can tell, the rules are:
Anyone can drive the route, regardless of ability or skill. Bring a co-pilot or don't.
Use any car you like. Bone stock, modded, full-on rally car, whatever. This is possibly the only rallying series where a completely regular late 90s VW Passat will come by right after a rally-prepped MK9 Evo, closely tailed by a Skoda Favorit wagon. No level of damage is too great to prevent you from completing the stage.
Roll-cage, crash helmets and other safety gear are entirely optional. Most of the cars new enough to have airbags have not disabled them. Additionally, spectators will stand directly on the outside of icy bends with no barrier or even berm between them and the cars understeering directly towards them.
The road is entirely ice-slickened, with ditches on either side. When you crash, the spectators will happily bundle in and get you back on your wheels, in the least co-ordinated manner possible.
Sometimes there are random stacks of tyres in the road. At first I thought they were to block off a side road from the main route but everyone drives around or through them so maybe they're just for kicks. If you can't avoid them, protocol seems to be to hit them head on at full speed, then carry them as far away from where they should be on the front of your car as revenge. Other times the spectators will build snowmen in the road between cars passing for them to aim at.
Sadly, it looks like for 2014 they tightened up the rules to stop the constant crashing, but luckily this doesn't seem to have reached the other sport I found, Czech amateur rallycrossing!
If you love seeing a Skoda Favorit understeer into a wall at 20mph (and I know you do), there's plenty of that here.