Does that really make a difference? I’d not worry about writing anything and putting it online saying “this can be used for evil so don’t do that”. But if I was approached by a criminal who asked me to write code for their criminal activity and I did so knowingly, then I’d expect legal consequences, possibly even if my code was never deployed at all.
The difference must be in whether or not there was a conspiracy to commit crimes or if there wasn’t?
In this case I don’t know whether this was purely open and no such contact between user and developer existed. But in principle I’d expect writing (almost) anything in the open to be safe.