“Assume it’s a question whether one may copy music for a friend. Half the poskim in the world say he may, and half say he may not. “
Not the best example because in most cases it would be illegal under secular law. Even if you limit the scope of dina malchutcha dina, people have gotten fined for doing things like that and if you do it on a large scale you can be prosecuted. Better to pay for the music.