During application creation JBoss Tools reports the following.

"Could not create application
We werent able to lookup your hostname (https://myjbossapp-myD2012020102.dev.rhcloud.com/) in a reasonable amount of time. This can happen periodically and will just take an extra minute or two to propagate depending on where you are in the world.
Once you are able to access your application in a browser, you can then clone your git repository.
If you cant get your application running in the browser, you can also try destroying and recreating the application as well using this Wizard.

If this doesnt work for you, let us know in the forums or in IRC and well make sure to get you up and running.

Forums: https://www.redhat.com/openshift/forums/express

IRC: #openshift (on Freenode)"

It was a user with an already registered namespace. On the web-interface (latest devenv, ami-c73cedae) I can see the application and later I can clone it.

As a side effect I cannot embed any cartridges to this application.