The Deebach packages can be installed on Korg keyboards, and they replace the Korg sounds completely. I.e., you cannot install them additionally, but you lose all Korg sounds as long as the Deebach sounds are installed. This has also been criticized in the German forum, they don't offer a solution where you could keep at least a part of the Korg sounds. (Of course you could always restore the original Korg sounds with a reset).
EDIT: So, what you hear soundwise is nothing from Korg, all from Deebach. The Korg PA is just a body shell (plus, I'm not sure about that, Korg's style data (definitely without style sounds)). Maybe someone who has used it can explain in how far the Korg styles are integrated into the Deebach soundset...