It says: "The Irish Wedding Dance is an original piano arrangement of a traditional Irish folk wedding dance by Nicholas Steinbach. The piece is an original composition but has its roots in Irish folk tunes."
So where did Steinbach learn the "traditional" tune? Or does his arrangement (or "original composition"?) merely "have roots in Irish folk tunes."
The music is copyrighted "2017," 35 years after the tune first saw print. So....