Your question goes to the heart of our discussions regarding traditional music. Woody Guthrie freely admitted that his songs were recompositions of older material. Were they original songs? That depends upon how you define originality. Obviously, the lyrics and themes he employed were his own. The chord progressions and melodies he set those lyrics to were often borrowed (appropriated?) from other sources. My personal opinion: Woody Guthrie only admitted to what songwriters have done for centuries. Every newly-composed song is to a certain degree a rewrite of existing material. An 'original' composition introduces a degree of novelty (originality?) that sets the song or ballad apart from any antecedents. I cannot offer a quantifiable definition of 'originality', but I know an original song when I hear it.