It was a promotion that Disney ran that had to be booked by last spring and the travel dates were late August - Sept. This is the 3rd year they have run it, I believe.
If you haven't booked it yet, it's too late sadly. If you booked it and aren't sure what it includes, there is a FAQ thread under the DDP forum at the top of the page.
Basically - you get the DDP free if you booked a package at rack rate during the promotional dates.