Hello Jos,
yes, that is right. The “msgid” has to be left as is. The “msgstr” needs to be changed to match your language.
I guess, you are working with UCS 3.0 for the translation. Yesterday, we released UCS 3.1. If you are almost finished with the translation, I suggest you continue. Afterwards, the existing translation files in the branches can be compared for changes and just need to be updated for UCS 3.1. The code can be found here: svn checkout http://forge.univention.org/svn/dev/branches/ucs-3.1/ucs/
Best regards,
Nico Gulden