Well after reading everything that this site claims to provide and they caim that after paying for the game and downloading it, if for whatever reason you need to re-download it you can. They also say that there is no limit to how many times you can re-download. They say that once you pay for it, the game is yours and you will have an online account.
"What is D2D Download Protection?
Being gamers ourselves, D2D knows that there are always those unexpected occurrences—like your hard drive frying or a virus infection—that threaten your precious digital content. D2D's Download Protection helps put those worries to rest! D2D allows you to re-download your digital game purchases at no cost. So every time you download from D2D you'll get a great game and peace of mind".