You are right. The site has just a few members now. If invitation code is required for sign-up, it will take ages to get a reasonable number of members.
Then who will send the invitation code? The existing members or the site admin? It would be practical if it is made clear in the form itself. No one is going to read the terms, policy, etc., unless these are very important for the visitors.

__________________
www.nexusinternational.biz