Their job is to decide when somebody has won the prize. They must reach unanimous agreement in order for the prize to be awarded. Anybody should be able to use the test suite to verify for himself or herself whether the prize criterion has been met, so the suite must be easy to run on a variety of popular computing platforms. Some people will try to win the prize, by submitting their animations and source code to the judges. When the prize has been won, the judges make an announcement, and the investors mail their checks to the winner.
Nobody pays more than they want to pay.
Investors may remain anonymous if they wish, announcing their pledges thru the judges but having their names withheld, or not announcing them at all. Assuming market forces really work, the value of the prize should fairly accurately represent the value to the nanotech community of the work involved in winning the prize. There is nothing in this scheme to prevent investors from welching on their pledges. They are bound only by the honor system, and prize contenders must understand this when they decide to try for the prize. For this reason, investors should only pledge amounts that they are sure they're willing to pay, even if they don't like the judges' decision.