As a general note, please use the email@example.com mailing
list for questions about using Jackrabbit.
> I have a short question: when I delete a versionable node, does JR
> automatically delete all node's versions ?
Use the VersionHistory.removeVersion() method.
> If not, how can I delete the remaining orphan versions.
Once you've removed all past versions and there are no remaining
references to the version history, Jackrabbit (since version 1.6.0,
see https://issues.apache.org/jira/browse/JCR-134) will automatically
remove also the version history node from /jcr:system.