This topic came up on the recent EE4J PMC call. The following questions will be reflected in the minutes:
We require an agreement with Oracle use to use the javax namespace. At present, we do not have an agreement in place, so we're limited in terms of what we're allowed to do. Getting this agreement in place is a high priority item, but--as you can imagine--there are a lot of high priority items that need to be addressed as we work through this period of transition. Your frustrations are understood, and your ongoing patience is appreciated.
At present, the publication of binary artifacts which include changes (or additions) to APIs in the javax namespace cannot be made available for general use. Changes to the implementation are permitted, but not to the APIs. My understanding is that this limitation applies to repo.eclipse.org.
It is okay for incompatible changes to be created in the source code (i.e. in Git repository branches).
Snapshots and releases can publish updates to binary artifacts as long as they make no modifications (or additions) to APIs within the javax namespace.