I recently set up a new site (hikethecanyon.org) on the Google App Engine running OpenBlueDragon. By default when you set up a new site on GAE (Google App Engine), you choose an ID for your application, which must be unique on their system as it also serves as the hostname of the URL like this: http://[your ID].appspot.com. For those that would like to use a different domain name, Google App Engine has mechanisms for doing so. In the administration panel of your application, you can add a domain and then choose hostnames from that domain that the application should respond to. However, it makes no provisions for serving the "naked domain".
Excellent step-by-step by Dave Shuck on how to get "naked domains" (meaning no "www" prefix) up and running on Google App Engine.