It's not really the camera controller that can be reprogrammed, it's the USB controller - there is a setting that the USB controller changes in the camera chip,

It's not really the camera controller that can be reprogrammed, it's the USB controller - there is a setting that the USB controller changes in the camera chip, but there is a nontrivial amount of logic done on the USB controller. Still, it's a very, very cool hack: they reprogram a microprocessor to send commands to another microprocessor and configure it in such a way that it enters a state where the pin that the LED is connected to is irrelevant.