Never mind, solved it!
Since my default locale is not English, I had to make an extra copy of all the messages_*_en.properties files and rename them to messages_*.properties.
I hope this helps someone else...
Also the example misses a
/themes/openremotedirectory with themes, so you either have to make a copy of another existing themes directory (e.g.
default) and rename it to
openremote, or change the value of PREFERENCE.PROPERTY_NAME