In order to use the Forums, you must register. If you try to reply or start a new topic, you see a banner in the upper right that asks you to "login" or 'register". Click on "register" and fill out the form. After the first time, you'll have to login in to post anything or to reply.
While this may be annoying to some, it is a security precaution that allows the administrator to block spammers. And we will attract spammers. It's only a matter of time.