I have a membership pin board-style bookmarking site. I would like to have a forum script installed and integrated with the site script. Only members of the main site should have access to the forum. Upon creating (and possibly confirming) an account on the main site, an identical member account should be created within the forum script. With session control, upon logging into the main site the member should also have the ability to post/reply within the forum. When users logout from the main site, they should be logged out from the forum as well. All regular member and admin features of the forum should work as originally designed. Forum can appear with its own header/footer, or with the same header/footer/css of main site if possible.
Please respond with forum you would integrate (so I may research its features), estimate of cost and time to accomplish integration.