So who was FP ripping off?
William Shakespeare. It's well-known that Forbidden Planet
was inspired by The Tempest
"Well-known"? Since the topic of this thread is to separate myth from fact, this is a good occasion to debunk this particular myth.
I recommend reading Shakespeare's actual work
. The protagonists in "Forbidden Planet" differ so vastly in their roles and actions from the characters in The Tempest
that it's most definitely not an adaptation (and neither an inspiration, IMHO).
It would be like saying that Pike is a carbon copy of Adams, Boyce is a carbon copy of Ostrow and Vina is a carbon copy of Altaira, which apparently is not the case.