Nobody has written anything that could be construed as Libelous. Yet. Insinuations are not libel and written accusations are not slander. You'll need to know the difference between the two. Also, you still have not addressed the language you used in your rules. Doesn't matter what you say to us here in the forums. Your written rules still can not be construed as legal with the current wording used. Change that wording and be more specific and folks will be less likely to make accusations against you.
Just a little history lesson here. There have been many attempts to steal content in the 3D and Poser community. Folks are going to be very wary of anyone who doesn't present a squeaky clean set of legal rules for any contests where rights of proprietary ownership of materials and content is concerned. Learn that fast and learn it well and you'll succeed in your endeavor. Ignore it at your own risk. When someone points out the vagueness of your rules, it's not slander (Or libel to be precise) it's merely our attempt at getting you to update your rules so they don't leave wiggle room for theft.
It is a miracle that curiosity survives formal education. - Albert Einstein