Street view is active, but only in specific (the biggest) cities. But as far as I can remember (please correct if I'm wrong) Google decided to restrict street view in Germany by themselves, not by a court's decision or something; AFAIK they only have been forced to allow people to blur people/license plates. And specific cars and houses/apartments if the owners request so (which they always offered internationally anyways) MS streetside was completely shut down for Germany though.
It's indeed a difficult topic, but I just googled (in German) for any relevant information on Mapillary and privacy concerns in Germany, and didn't find anything except for one discussion on OSM forums:
https://forum.openstreetmap.org/viewtopic.php?id=55201 (the discussion is in German, but you might use Google translate or similar to read.)
I guess as long as nobody complains it's fine. And if by any time someone complains and Mapillary would become restricted or even forbidden it'd be an automatic process, so I don't think you have to worry. But I'd recommend to manually look through all pictures to make sure everything's blurred correctly.
Edit: This law might be interested aswell:
It roughly translates to:
1) It's allowed to duplicate, publish and publicly show works* (in this case photos) of things that are permanently located at public ways, streets or places; the works* can be taken by using drawing, graphics, photography or videos.
* Don't know the correct translation, I hope it's still clear.
2) is irrelevant for Mapillary.
A long, german detailed description of the "Panoramafreiheit" (Freedom of panorama) can be found here:
English version (covers Germany just minimally though): https://en.wikipedia.org/wiki/Freedom_of_panorama#European_Union
Second edit: Oops, just saw how old this topic is. Maybe it's useful for someone else though.