Is running away illegal in Pennsylvania?

I have a friend who is considering running away, in conjunction with various letters and meeting with his father in order to deal with his issues at home. The issue, to be a little more clear, has to do with domestic abuse between his parents, when he brings up the issue, he gets yelled at, and currently, he is afraid that if he pushes the issue, he'll get hit, without an answer. The two of us and another one of our friends determined that in order to really get any result, he'd need to drop a note, aggressively discussing and questioning the issue. Finally, we decided that it would be opportune to insure an indefinite "cool down" time for his father, and that left at a friend's house, he would promptly be recovered.