When used by a boy or man about another male in a non-sexual, non-romantic context, especially when it's a friendship between a girl and a boy, they use the term "guy friend" so it would avoid confusion with the sexual or romantic meaning.
Though nuanced, there is a significant difference between girlfriend and boyfriend, and girl friend and boy friend. In a strictly grammatical sense, a girlfriend or boyfriend is an 'individual of significance' with whom one shares a relationship. A girl friend or boy friend, however, is simply a friend identified on the basis of gender. Since the pronunciation is the same, these words may occur to be false friends.
