..I am quite sure that it is protected. Another thing is if anybody would sue you if you use it (which doesn't mean it's ok to copy it
)
It is funny and brings it to the point. Probably a good starting point for beginner courses in electronics.
We were told a water-analogy:
A bucket of water is attached with a waterhose.
The height above ground of the Bucket is the Voltage, the water-flow through the hose is the current and the diameter is the resistance. Somehow I prefer the cartoon-style