Phew! It was tricky but I managed to track down the rules for competition. They are here: http://www.silat.be/oldsite/Engels/competition.htm
Basically, the scoring areas are the Chest, Belly, Back & Ribs. Cord was right, it doesn't seem as if head contact is allowed.
You can attack with the hand, arm, elbow, foot, knee & leg.
Sweeps, throws, takedowns, trips are allowed (in fact you get a big score for doing so, but only if you take the opponent down).
KO's are allowed, as long as they are by a valid attack.
The rules are far from comprehensive, but they are a solid foundation.