I write songs in the (a?) traditional style. The words are original (well, actually all the words are traditional - it's the order of the words that is original!) but the tune often arranges itself round something in my head that fits. That may be original, may be traditional or maybe from someone else's copyright song - and they may well have borrowed the tune from somewhere else and only really written the words. It's not about money, but as said above, credit should be given where due if possible. That seems much easier to do with words than tunes.

Andrew