Hi Matthias,
unfortunately I have no experience if it is possible to extract a phar file on a server without the phar extension, but I could temporarily provide you the German files (tomorrow).
Beside that, since we host osTicket on our own server, I never tested to use the extracted files and not the phar, so no experience here either. When I find the time I will test it also. Maybe tomorrow, maybe before Christmas, maybe before the new year, maybe in early 2015, just don't know, but definitely going to test it ;) Finally, as a translator and proofreader of the German language pack, let me know when you are interested in joining the German translation over at crowdin (i18n.osticket.com) or when you found a typo / error / bug in the German translation.
Cheers,
Michael