To make things clear about the site, http://wordpress.org/ is not a blog -- that is, the whole of it is not running on top of WordPress. The links along the top (About, Docs...) are separate sections of the site, and not categories as on a blog.
http://wordpress.org/development (Dev Blog link) is a blog running WordPress.
In simplest terms a WordPress blog is a collection of posts under one or more categories. When you visit the home page of a blog, WordPress as designed will display the most recent or newest posts, independent of category. When you click a link to a category page, you're passing the $cat variable (for that category) to WordPress. So by setting the $cat variable for the home page, as done in the PHP code above, we're in effect turning the home page into a category page. Issues of layout and content may likely crop up, but only if they normally do so for category pages on your site.
To have *static* pages that exist outside the normal flow of blog posts and categories (which it sounds like you may be after), see this page:
Version 1.5 of WordPress will offer this as a built-in feature called Pages. For that, see: