It seems that DC Universe Online subscriptions are locked to the game discs, so don’t bother picking up a used copy of the game. Sony Online Entertainment stated to Lazy Gamer that “once the PSN key has been consumed with a disc it cannot be resold/replayed with the second user adding a sub – only the original consumer can use that account.”
“Disk and account are one,” SOE confirmed.
Thanks to Lazy Gamer for the info.