Can you typically call off a kos? As in let's say player A calls a kos on player B and it goes like this: Player C sees this and marks B as Kill. He did not see the Nos and thus did not know that the KOS was called off. Now I only have 3 questions: Is it RDM when C kills B? Can KOSs technically ever be called off? If it causes the death of B is it a false kos and does A need to be slayed?
It is not RDM on player C, but on Player A. If at any time a call out results in a person's death without the killer acknowledging the call out, it is RDM on the person that calls it. However, if the killer acknowledges that you called it off by saying something like, "You can't call off a KOS!" Then it is them who RDM'd.
Correct. Like, if he gives acknowledgement of the call off by saying, "You can't call of KOS's" or something of that nature, then they acknowledged they saw it being called off and went on to carry out the kill.