Those who received some house credit, from participation prize or side competition or daily challenge, probably have some some directbet coins in the wallets, you can exchange them for Bitcoins and withdraw(1mBTC = 1000 directbet coins). Shouldn't take more than a few minutes and some people say Bitcoin will be worth 1M in 10 years, so every bit is worth.

Why not start the competition funded by the users, then seek a sponsor later? This competition may be expensive, so maybe a sponsor won't be willing to pay everything.  With completely news rules, of course.