Hi Don, The other side of the coin is that songwriters can be ripped off. I was informed by a fellow Mudcatter that an original song of mine, Hush, Hush (AKA Smile in your Sleep)had been recorded recently by Maddy Prior and the credits claimed she had written it. I contacted the record company who admitted a mistake but they had meant to say that she arranged it as a traditional song. I could prove the song had been published in book form and recorded previously (1966 actually!) so I will get my royalties. The songs you mentioned, however, are traditional and can be recorded by anyone as long as you put Trad; arranged by yourself.
Good luck,
Jim McLean