Is it OK to contact a person whom your friend has an order of protection on, in a position of a third person?

If you mean, to act as a go-between, then I'd say that person should watch that they don't invalidate the protection order. Protection orders are granted because one person feels threatened by another person. A judge listened to the evidence and agreed. If the friend with the order wants to communicate with the person she has a protection order for, then she risks losing the order because, obviously, she's not afraid anymore. Her friend, the go-between, risks having the person she communicates with take out his (it's usually a guy) anger and frustration on her. "The friend of my enemy is my enemy." kind of thing. I wouldn't get involved unless I wanted my friend's problems with her ex-whatever to be my problems.