WordPress.org

What if I have Wordpress v2.6 or below?

You can use the previous version of this plugin (v1.2.1) with the older style Wordpress UI (ie. pre Wordpress 2.7).

But I can still access posts and other blog functionality if I manually type in the url

Yes this plugin does NOT restrict access to any part of the Wordpress backend. It just hides elements from users to make the backend simpler.