1971 D Kennedy Half. Poss. DDR Or Double Strike? At Wing And Lettering

Well business strike coins are only struck once. So its not a double strike. What you are seeing is the most common doubling on coin, Machine Doubling. Not a premium coin as they are so common to find. On Machine Doubling, the die is normal, but the machine causes the doubling, just like what we see on your coin. On a doubled die, the die is doubled, thus the term doubled die.

Note the doubling. It is not on the outside edge of the coin, but in the center of the devices. But a doubled die can also show Machine Doubling. Because the machine causes the damage. But a doubled die creates all the hub doubling on the coins the same each time. (Except allowing for die wear) The answer to both of your questions, it is Machine Doubling.

The movement is called Machine Doubling. The machine caused the fresh struck devices to be altered. On a doubled die the doubling is on the die. So the term is calling it correctly as a doubled die. But if the machine causes the doubling, it is not a doubled die. But even a doubled die can show Machine Doubling. (not desired by true variety collectors) Here is an example on a doubled die:
These are all from the same big DDO-001 for that year. Note all the dates are showing hub doubling (that causes a doubled die).

But note the yellow arrows? They are showing where after the strike the machine kicked in the shins those affected areas. A grading company accepts Machine Doubling as a normal event. Doesn't consider it when the coin is graded. But to a true collector, it is as unpopular as acne on a teenager. (consider them a distraction and if used as a teaching aid, just adds confusion. So they view them as a problem coin. I know that is how I view them)