I'm not entirely sure, but I think originally when they first made WDW Annual Passes the first ones were "charter members" and could renew al a lower rate. It really has nothing to do with DVC, I think they are just saying if you had one of the origianal "Charter APs" you wpay the same rate as any other DVC member.
But the original "Charter Members", if they are not a DVC member, get a cheaper renewal price than non-Charter members.