Update: the Profile Service, part of the AppCloudServices module, has been updated. It now exposes a more extensive user profile, including the user's email address. A new version of the AppCloudServices module has recently been released to the App Store, which contains the new profile service.
Previous answer: The URL that is shown is the OpenID identifier of the user. At the time of writing, in the latest version of App Cloud Services, v.1.1, it is not possible to get the user's email address. You can only get a user's display name.
You could ask the user for any further information that you need from him/her after logging in.