I think you are being far too harsh on your definition of folk. By my reckoning it is relevant, because the passage of time as infused it into the folk tradition. True it was written by known people, as were many of the shakespeare songs I posted. Are those not allowed?

Many of the songs I have posted here and others who have posted here have been "Literature". Literature would include poetry/verse by Ben Johnson (Caveat for Cutpurses), Marlowe (Come live with me and be my love), etc. Are those not part of what is generally considered 'folk'? I dont get it.