The old forum has now been disabled. In the last 2 years there has only been a handful of posts other than from spammers so it is no longer worth the effort trying to maintain a spam free forum.
The new site design is more content oriented, however still allows for some discussion if desired with registered users able to post comments on posts. Note old forum logins are no longer valid, you will need to re-register. Your first comment will be held for moderation as an anti-spam measure, though subsequent comments should appear straight away.
In order to create new posts you will need to request membership of the content editor group, see here.