A few posts back you mentioned the 'stationary engine' thing relating to a ferris wheel. A ferris wheel is full of people, who paid to be spun around. It could be powered by a water wheel or a hand crank, the passengers could still be injured or killed by unsafe equipment or negligent operation. Hence inspection and licensing. Working the controls of any piece of equipment, car, locomotive, ferris wheel, or rocket launcher is 'operating' it. A ferris wheel is not a car is not a suck pump, so different licensing categories exist.
Someone else used the Ferris Wheel ~ I prefer to use the “bumper cars” ride having much more familiarity with it ~ Ferris wheels give me a stomach ache. Most of the other rides at a carnival are pretty much like swings, and some are like trains, repleat with rails and such.