There's another good way to eliminate these concerns: don't have big prizes.
When I hosted a hackathon last summer, I put no limits on projects but the max value of the prizes was $25. With prizes so small, there's no incentive to game the system nor is it grossly unfair to let people work on something they'd already started on.
The goal was purely to work on something cool for a day with like-minded people. One guy brought on a voice-controlled Nest lamp he'd been working on, another built an Arduino step-counter, a third took a crack at writing a basic chess AI.
We provided pizza and beer and just let everyone loose. It went great and there were no hard feelings.
When I hosted a hackathon last summer, I put no limits on projects but the max value of the prizes was $25. With prizes so small, there's no incentive to game the system nor is it grossly unfair to let people work on something they'd already started on.
The goal was purely to work on something cool for a day with like-minded people. One guy brought on a voice-controlled Nest lamp he'd been working on, another built an Arduino step-counter, a third took a crack at writing a basic chess AI.
We provided pizza and beer and just let everyone loose. It went great and there were no hard feelings.