It's going to get stolen and redistributed no matter where you publish it. You can make bit hard, but you'd probably end up putting more effort into the protection system than the fame and you'd need at least one server running 24x7 to authorize it.
Problem is, you're thinking about it wrong. Freely distribute the executables, but have it come up with a machine specific license once it starts. Priates will help you by distributing the executables, but anyone who wants to play it in full will need to purchase a license. At least until someone hacks the code to circumvent the license.
Purple