100% of the ad revenue is yours.
I think this paragraph is open for interpretation:
Wikia, a commercial counterpart to the non-profit Wikipedia, will go even further to provide customers -- bloggers or other operators who meet its criteria for popular Web sites -- 100 percent of any advertising revenue from the sites they build.
I think that means that only the ones that qualify as being "popular" get the 100 percent ad revenue. Or maybe it means that only the popular operators are eligible for the Wikia offer.
However, I'll remove that part from the original post to try to avoid giving misleading information.