You can find the full source code for this website in the Seam package in the directory /examples/wiki. It is licensed under the LGPL.
Assuming you have Eclipse, the JBoss Tools plugins, Seam and JBoss properly installed, everything you need is in the Seam and Hibernate perspectives.
Start in the Seam perspective and select New > Seam Web Project to get started. Follow the wizard and let JBoss Tools create a new project for you. Now select the new project and choose Run As > Run on Server from the context menu.
Now you can get started writing code, try out the New > Seam Action wizard if you need help!