Interop is a good goal. However, I frankly don't see us ever achieving "total interoperability" by exclusively relying on trademark enforcement as leverage.
The only path I see currently towards the type of interop that would allow for workload federation across providers is if there was an upstream project, whereby various providers would proactively write and maintain connectors into a central auth system... kinda like an "openstack native rightscale." Those deploying openstack on-prem would then be able to leverage this module to federate on-prem environment with all the providers that have a functional driver. I.e. just like you have multiple storage provider drivers to cinder, we need services providers to write and maintain drivers against something in OpenStack. I've seen discussions and even blueprints on federated keystone in the past, but am not sure how much progress has been made... Thierry maybe you know more?
I.e. there has to be a technology solution to back up administrative action. Not just trademarks and definitions.
Thoughts?
-Boris