DP's are developer points. They were set of matching points given to buyers as an incentive. For example, if you purchased 160 BLT points, you got 160 extra points to use at SSR or a DL hotel, or you could bank them with RCI for a futre trip. They carried an expiration date of October 3rd.
When the new incentives came out April 1st, they eliminated DP's as an incentive so I don't believe they are still available.
Of course, you can call Disney and ask to speak to a guide and then can tell you for sure.