You can rent the points off of another DVC member looking to rent, at different websites than this one. OR you can pay cash for the room to make the vacation as long as you want. If it's a WDW vacation, and you're staying at a DVC resort, there will be a DVC discount.
Bear in mind, however, that if you opt to pay for the room, you can't mix points and cash for the same night. In other words, let's say that those 25 points you're looking to rent is for room that requires 35 points for the night you want. You have 10 of those points, but you need another 25. There's no way to break down the room so that you can use your 10 points and pay the balance of the room, for the night, in cash. You'd either have to rent points, or pay for the whole room and bank those leftover 10 points.