If you are referring to this page -> https://www.google.com/a/cpanel/your-domain/UserHub, then you can't. apart from google apps applications, only custom apps added from the market place appear here (as far as I know).
I guess you could get around it by adding your app to the marketplace (with a fake, but valid manifest.xml), but not submitting it. then adding the app to your domain from the draft marketplace listing. I haven't tried this though -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
