Currently new site registrations are done only by the administartor. This is because we've been getting more than one spam registration every hour, so open registration won't be enabled until that spam problem has been dealt with. Just email the site via the contact form if you'd like to have a free account so you can either subscribe to a future newsletter or post on site forums.
If you use an invalid email address, or your username suggests you're a spammer, you won't get an account.
If you are a spammer, you can save yourself some time. You will never be allowed to post spam and have it left intact on this site.