The law tends to address this in various ways. I don't know how German law does it, but usually there is a fairly exact description of what stopping for a traffic signal entails (e.g., the driver has to be present in the vehicle). Also most jurisdictions have a catch-all law that prohibits dangerous behaviour in traffic.

So yes, there probably is a legal obligation to keep moving. If you went there and stood in front of the light for an hour a friendly but stern police officer will — legally, and within his mandate — instruct you to move along.

There is, though. General red with a specific green (the arrow pointing to the right) means you can stop, but once a car behind you wants to turn right, you need to turn right too in order to keep traffic flowing.

The charge is usually "public nuisance" or the local jurisdictional equivalent.

In case anyone is unfamiliar with the concept of public nuisance as a crime. It's pretty simple, "things that cause significant enough trouble for other people". Its the common sense escape hatch option for law enforcement being unable to see any other crime.

I would guess that it would be "Behinderung des Straßenverkehrs" (obstruction of traffic).

They could solve this problem by turning it green every now and then, though.