The forums are as you remember them from the past, but with a couple of key differences. Firstly, the forums are run alongside the site, not within it (see the sign-up page at the bottom of the article).
Secondly, the forums are not open for public browsing. That means, if you want to browse or take part, you will need to register on the forum (note that your old sign-up details will not work). Finally, membership is being limited, so sign up as soon as possible, as membership will eventually close to control the number of people using it (and to keep running costs down).
That’s it. The rules are on the forum and things are already moving. So if you want to take part, sign up now.