Visited on October 12, could not charge.
I was able to activate the chargers with the eCarUp app, but the car said there was a problem with the charging station or the car electrical system, given this was the only station I was not able to charge at that day, it probably wasn't a problem with the car.
Given the branding it looks like the chargers are intended to be accessible by the public, but it's not clear if that's only outside business hours or anytime. In the eCarUp app it just says "Laden sie bei uns auf dem Besucherparkplatz" in the description. The sign on the wall says you can only park outside business hours, but makes no mention of the charging stations.
On eCarUp there are 2 additional stations listed, but they seem to have never worked. I didn't see any sign of additional chargers around the building. Perhaps those are the IDs of older stations that were swapped with the ones currently in place.