Allen, I admit I only read the abstract but I don't see how the Nature article relates to our discussion here. Since every atom is, effectively, a perpetual motion machine, that is not a big deal at the molecular/atomic level. The hard part has always been to create more energy from less energy (including mass equivalent energy), which would violate the law of conservation of energy/mass. This hard part includes creating a perpetual motion machine on a larger scale in which friction dissipates a nonzero amount of energy and the motion eventually peters out. So far I have not heard of anyone who has proven theoretically or demonstrated experimentally an exception to the law of conservation of energy/mass. Special relativity says energy has mass and can be converted into mass and the mass back into energy, and this has been confirmed experimentally many times. Ignoring this effect could lead one to believe erroneously that energy had been created when in fact it had just been converted from mass.
So have fun if you want to try to build such a machine, but be honest with yourself and others. You might want to start with basic physics like this:
http://en.wikipedia.org/wiki/Conservation_of_energy but be aware it gets a lot worse, fast, once you start dealing with quantum level phenomena or special relativity (E=mc^2). Leave general relativity to the big boys and girls, and remember you can't fool mother nature.
Let us know if you succeed. We want to hear it here at PSW first!