I think what 3kings meant is that free forumhosts (like proboard,
ezboard, etc.) tend to require reader registration. They make
money not just by selling adspace but by selling your email addy
to marketers, though they ask you upfront "if you would like to
receive news" on fitness/health/mail order cheeses/whathaveyou
during the registration process.
GT exists on paid servers, so that the owner, Eric, is free
to dictate an open browsing policy... on his hard-earned dime.