The Rooftop Singers collected royalties on Hughie "Gus" Cannon's "Walk Right In".
Lou Gottleib of the Limelighters collected some royalties on Uncle Dave Macon's "Rock About My Saro Jane".
The melody to Bob Dylan's "Masters of War" is Jean Ritchie's song "Nottamun Town".
Of course both Dylan and Woody used other available melodies for their songs. I don't recall either of them being sued.

The point is that there is a difficulty in determining what is an original source for a folk-type song. Now show and jazz songs are different. These can be quite unique. If you rewrite an Irving Berlin or Jerome Kern song, you will hear about it from the publisher.

By the way, Malvina Reynolds wrote "Little Boxes" to the tune of a popular song of the Forties called "There's A Pawnshop on the Corner In Pittsburgh, Pennsylvania".