See, the real problem with a licensed derivative IP is that, should your license be revoked and the terms thereof not say otherwise, you suddenly have a USELESS IP, unless you sell that IP to either the holder of the source IP, another of their extant licensees, or are sufficiently derivative as to be a wholly separate IP, or the whole of the derivative is done for comedic intent.
a change in media doesn't create a difference in the IP for purposes of determining derivation... although in some odd situations (Lyric sheets vs score vs performance recording vs midi file, for example) variations in media may be derivatives of each other AND the source...
Since it is clear that the IP of the DGP materials was not only derivative, but also subject to terminable license, Roger has a lot of useless data he purchased. Useless, that is, to everyone except QLI, SJG and MWM.