So I gave it a go, and the dlc showed as corrupt in the Storage menu.
Same thing happened to me. The quick fix is to import the package into the program and re-sign it.
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!