Here is the situation:
I own a Google Apps for Business account.
I have two domain names registered :
google app engine does not allow mapping naked domain. you can use a redirect from myapp.com to www.myapp.com.
"Due to recent changes, App Engine no longer supports mapping your app to a naked domain. If your domain registrar supports URL redirects, you can redirect from http://yourdomain.com to e.g http://www.yourdomain.com or http://appid.yourdomain.com."
http://code.google.com/appengine/kb/general.html#naked_domain