Okay – i woke up with this blinding idea that should answer all the above questions (apart from ownership which i’ll come to) – although before I share I’m debating whether to shatter Rooster’s bubble or not 
Anyhow, its quite simple. Cookies! When someone enters the forum from your site, a cookie is set with your site ID that is unique to your site. Every page a player loads reads the cookie and runs random banners from a text file of links that each site provides me. It also changes the logo, keeping the forum identity generic but adding your site:
IE: The Global Casino Forum @ Games & Casino
OR: The Global Casino Forum @ Oggs.com
etc. That way, your users always see your site name, all links are set back to your site and all banners are yours, but posts are shared. In theory, this may also allow me to MOD it so only the forums you want are shown, but I’m not 100% sure oon that one.
Just as importantly, the data is centralised so its only in one place – thus the registration “legal” form can cater for the fact its still in one place but displayed on multiple sites or in feeds at a later date.
This also means in BB1’s scenario, the players know they have signed up via the Global Casino Forum so the once monthly mailing will be from a recognised source also.
Anyway, i’m gonna go practice this Cookie theory….may have something before half of you wake up 
Cheers
Simmo!