Erm .. even if I am not talking any money from them and its not on 'chance'?

Basically, I'll just ask them to sign up and integrate a piece of software in their games which will track their game's performance. In the end, the games with the best usage stats would win. The data will be open for everyone to see so there are no concerns about the fraud.

Do I still have to follow lottery/gambling-related laws? :|