Every song must have had an author at its origin. It's just that the power of the song becomes greater than its association with the author, which in time gets overlooked as it is passed on. Consider John Connelly's Fiddlers Green; I have heard several references to this being a traditional song. Obviously it's a great song. It means of course that the author no longer receives any credit for its creation (financial or otherwise). Maybe others like Rare Ould Times or When We Go Rolling Home may quickly become "trad". It depends on how long we hang on to the authors name when executing the oral tradition.