I don't think there should be any music issues at all. From what I've read, the songs performed by the Splits were original songs specifically written, produced and recorded for the show. Yes, some sort of compensation would be required for the song writers and performers on the songs, but as far as I know, the songs themselves are owned outright by Hanna-Barbera. Looking at both the Deca album and the Kellogg's singles (I have the album and both singles), all are copyrighted by Hanna-Barbera. They all also say (and this is most directly related to the actual songs themselves) A Past, Present and Future Production by David Mook for Hanna-Barbera Productions, Inc.