JBoss RichFaces 4.0.0.Final is nearing gold status. Therefore the team now published a RichFaces Showcase application using Google´s App Engine. It can be found here:
If you want to try out the latest release candidate, RichFaces 4.0.0.CR1, you can also check out this article on how to use maven to include the neccesary libraries:
Have fun trying.