If it's anything like the picture, the reason right turns are allowed is the green arrow (it roughly translates to "when red, right turns are allowed if you don't interfere with other traffic"). I strongly doubt random towns in Germany can bypass the StVO (the laws which govern public roads).
EDIT: To clarify, I was born in Cologne, which is on the opposite of Germany, and green right arrows exist here as well and they are part of the material you learn for taking a driving exam.