I have published this image as author under the Creative-Commons-Licence CC BY-SA 4.0.. This means that free online usage outside of Wikimedia projects under the following terms of licence is possible:
The photographical reproduction of this work is covered under the article § 59 of the German copyright law, which states that "It shall be permissible to reproduce, by painting, drawing, photography or cinematography, works which are permanently located on public ways, streets or places and to distribute and publicly communicate such copies. For works of architecture, this provision shall be applicable only to the external appearance."
As with all other “limits of copyright by legally permitted uses”, no changes to the actual work are permitted under § 62 of the German copyright law (UrhG).