Building the Website
The website is produced with Apache Forrest. It allows you to build a reasonably good looking website without a whole lot of work. There's no need to develop your own menu and template system. You provide the content and it draws the interface around it.
This site is currently built with Forrest version 0.6. Please read the Forrest website for installation instructions. After installing Forrest you need to get the website project. This is available from the same git repository that the main source code is, it's just a different module, www. Checkout this module and then decide if you want to build the generated content like javadoc and translation information, or just the static site. To build just the static site simply run forrest from the top level directory. This should produce a copy of the website in the build/site subdirectory.
To generate the complete site, a copy of the driver source is also required since several parts of the website are generated from the source code itself. Checkout the driver source into a subdirectory of the www module. From inside the top level directory of the newly checked out www module, run ./scripts/buildSite.sh. This will generate all of the content needed and from then on you can simply run forrest to build the static content and see modifications you've made.
Adding a Page
To add a page the easiest thing to do is copy an existing one from src/documentation/content/xdocs and ripping out its content. Then you need to add the new file to the menu system listed in site.xml. A good place to look for examples is Forrest's own site and the source it comes from, their subversion repository.