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.
Most of the Seam example applications work with JBoss Application Server 5.x as is. Seam 2.2.0 is the recommended version for use with AS5.
The setup required to use JBoss AS 5 is exactly the same as with JBoss AS 4.2.X
Note that jpa example has AS5 specific build target - jboss5
Now pick one of these apps and change the pages and/or source code in your Seam's /examples/<app-dir> directory and redeploy the application by calling ant deploy - see how your modifications affect the application.
If you would like to understand some of the details of the Seam, AS 5 integration take a look on the JBoss wiki and specifically What is JBoss-Seam-Int
Seam's now target's JBoss 5. All examples have been tested and work with JBoss 5.