You don't necessarily need to host the other apps on appspot, if what they are providing is web UIs... you can serve them from your appspot as a proxy. The pages you serve will benefit from your authentication and will be able to access your REST APIs.
I've developed this open source project with a similar approach for research apps: http://cloud.addama.org. It ties a variety of apps running outside of GAE through a service registry running on GAE. The registry provides the security concerns and standardizes the REST APIs. -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.