Most of the pendulums you see in museums and on display are rigged with motors and elecro-magnets. Real Foucault Pendulums are powerless and need to be manually reset several times an hour lest they stop due to air friction.
Also, for the FE explanation of the Foucault Pendulum, lurk.
This is irrelevant, of course, since nobody is suggesting that the Foucault Pendulum is a perpetual motion device or somesuch, merely something to demonstrate the rotation of the Earth. If you're suggesting that they are intentionally rigging it to move as if the planet is rotating, well then we're running back into conspiracy territory.
I checked the link, and here's what I got:
"[Explanation of how the pendulum is theorized to work on a globular planet]
The above is very ingenious and very plausible, but unfortunately for its character as an argument, the evidence is wanting that the earth is a globe at all; and until proof of convexity is given, all questions as to its being oblate, oblong, or entirely spherical, are logically out of place."
So, he essentially seems to be saying that the pendulum cannot be evidence of a rotating globe because the planet is not a globe. Was this person an actual scientist?