ODJO for iPad supports all tracks purchased on the iTunes Store with the following restrictions:

Apple Music: Tracks added to your library via Apple Music can not be played. Unfortunately there is no way for 3rd-party apps such as ODJO to play songs from Apple Music, Apple’s music streaming service. This also applies when songs are downloaded onto your device from Apple Music, as the downloaded files will be DRM-protected.
DRM protection: Older tracks purchased from the iTunes Store can have DRM protection and can not be played. To play DRM-protected songs please upgrade your existing songs to iTunes Plus in the iTunes Store.