Theres no real point in a different language at its current stage, in the future however I can see it being a viable request.
It should be easy enough for anyone who understands programming and can speak both English and German to translate, then compile it for use, if you know anyone like that with time to spare im sure they can help you out.
The majority of minecraft users speak or understand English, so a German minercpp would limit the number of users able to use things such as /help.