"
free dining" never has anything to do with
DVC, so you'd probably do better to check on the dining forums.
some people probably get codes by email or mail that give them "pin codes" (like you use to access an ATM) which qualify them for XX% off resort reservations or "free dining." if they get a code for free dining, they have the option to call disney and book a package = book a room at rack rates (i.e. always for cash and
never for DVC points) + buy tickets to get the dining plan thrown in for "free."
disney gives their codes out randomly, though and you can't just call up and ask for the deal or use someone else's code since it is tied to their name and address.