I'm running several apps on Google App Engine. I am using the UserService for Authentication to be able to send emails on behalf of the user etc. and OAuth2 for API authorization.
I am now trying to publish the apps on the Google Apps Marketplace, but I received an email telling me it is required to use OAuth2 for authentication.
As I am just using the supported Google stack I assume there is a way to meet the requirements for publishing my apps on the Google Apps Marketplace but right now I'm stuck.