I bet that Thomas and Patrick could do something like have dynamically created tests, where there are multiple versions of an exploit, so that they test the same skill but in different ways. You might have a challenge that tests whether you can do SQL injection, but the tables may differ. Overrunning a buffer (as Patrick mentioned in his post about Microcorruption) could depend on different payloads.

I naiively believe that things could be varied enough that you would need to understand the concepts rather than paste answers, in which case "cheating" would mean "learning", and is basically something they say they want you to do. I'm not sure how hard it would be to get to that point rather than being vulnerable to Bob the Super Coder posting walkthrough screencasts, but I trust that the founders are already savvy enough to have been thinking about that.