A long time ago, I created a free Google App for a client on appengine.google.com (http://imitatorgwt.appspot.com).
Now my client wants more computing power - which requires to enable billing. But, I want to let my client pay for the app.
When I tried to enable billing through my Google account, I was asked to give my personal details.
How can I transfer the ownership of the app to my client, so that he will be able to do the billing without my intervention?
NOTE: I don't have access to all the source code right now, so I want to transfer the application "as is" - and not upload the code again to a new server.