The forum pages connect to Facebook because we have Facebook Connect.
As you can see at the top, you have the connect button and when posting a reply, you have to option to publish to Facebook if your accounts are connected.
This site is not compatible with NoScript. We also use the YUI (Yahoo! User Interface) library hosted on Google's servers for complex functions. This reduces load on our servers since they are using a distributed cloud computing method. This lets you do things like perform in-line editing and access drop-down menus with limited amount of code. We also use Google Analytics to anonymously gather statistics to improve the site. No specifically identifiable information is disclosed to any 3rd parties. See Privacy Statement. Most of the time it is used to give us an indication of how many people visited the site on a given month, and how many of those visitors are either unique or returning.
As Mitchell stated, the site accesses Facebook APIs to allow you, if desired, to link your profile here with your Facebook account. As more forums role out this feature, the millions of people who use Facebook create the possibility of a "universal login" for many different websites. Some more notable sites have started using these APIs, and they pose no security risk to you.