Maybe not quite a scam, since they are not taking money the minute after they they told you they wouldn't, but they're not quite honest either. Everything I can find on them says they park a domain the minute it becomes popular, unless you paid for it. They seem to have a ton of information on policies and this fact is probably buried in there somewhere.
While I personally think your site could be very interesting (seems a bit incomplete at the moment) I doubt you have to worry about the 500 visitors/day it will take to get it removed. Still, there could be other reasons they may decide to park your domain.
If you want something that is more certain, the big name blog sites and wiki farms would be a good place to look. My personal preference, and what I think might be the best one in your case is to get a wiki. Wikispaces and Wikidot (where I have my own site) would be your best bets because they allow you more control over how it looks than the more popular Wikia.