At first glance your forum appears to have only two boards, "Announcements & updates" and "Old News". However, I believe that most forums are probably just not visible to guests. If you're wanting to get new members then you might want to try letting them view the boards to see what you have to offer first, because a forum not viewable to the unregistered really discourages people from signing up.
I've been to a few forums that presented me with a "You must be logged in to view the forum" message and some that just didn't show me the posts, and I never signed up to these. On a rare occasion I might want something specific that I know is on that forum such as a tutorial I would like to read but otherwise I don't waste any time registering if there could possibly be nothing interesting there at all.
I'm aware you might think that if they can see everything without signing up, then they might not sign up at all. This is true, but even if those people did sign up so they could view, would they post? No.
Here's an example:
Let's pretend that you've opened a brand new PHP tutorial forum.
A person named Bob stumbles across your forum that lets you read all of the PHP tutorials without signing up. Bob reads a few useful PHP tutorials, leaves, and never returns to the forum because he was able to read everything he wanted to and didn't have to sign up.
Now, let's imagine that your PHP tutorial forum requires registration to view. Bob (yes, the same Bob as before) stumbles across your forum, but Bob can't view anything because he needs to sign up first. Since Bob knows you have some useful PHP tutorials, he registers. After logging into his newly created account, Bob reads the PHP tutorials he signed up to see. After he is now a professional PHP programmer due to your awesome tutorials, Bob leaves, never again visiting your forum.
What's the same?
In both of these situations, Bob reads your tutorials but does not come back to your forum.
What's different?
In the second situation, Bob registered, but only so he could view your PHP tutorials.
So, in the second situation he signs up. What's so bad about that?
Well, nothing. You now have one more forum member than before, right? But what's so great about having a member that doesn't post? How has your forum benefited from that member?
You may have a higher member count, but Bob still only read your tutorials and left. He didn't bother posting and didn't bother coming back, either. Members that don't ever post and don't come back to your forum are of no help to your community.
A small group of active users are more beneficial to your community and its members than a large group of inactive users.
By letting people view your content as a guest, you will have a more active user base because the people that sign up will do so out of choice, not out of requirement.
