Dear Greg
At the moment the idea of release for the NHS is a clinical content specification - these releases are in subversion too. They are not released for systems as yet.
We are moving to have an official openEHR release site which will be a collaborative authoring environment - it is up already but only being used by a few people who are testing it. We have vetted the NHS work to some extent and are taking a more strategic position on how to design the archetypes. We will be calling for participation soon.
Cheers, Sam