As for the reprinted editions of Slave Songs of the United States, there have been at least four known to me.

(1) New York: Peter Smith, 1929, 1951.
(2) New York: Oak Publications, 1965. With foreword by Irving Schlein. Guitar chords and music (piano arrangements) editing by Jerry Silverman. Illustrations added. Only the preface is a facsimile reproduction.
(3) Baltimore: Clearfield Company, 1992. With a new introduction by W.K. McNeil
(4) New York: Dover Publications, 1995

I think (3) & (4) are in print now.

Masato