+++ This bug was initially created as a clone of Bug #34556 +++ The current Developer Reference (http://docs.software-univention.de/developer-reference-4.1.html#join:libraries:shell) states that messagecatalogs can only be registered together with --udm_module, but as of Bug #34556 that is not true anymore.
This bug hasn't seen any update for several years. I close it. If you still see a need for it, you can reopen the bug. Please add an argumentation about why it's important to take care of it.