The current formulation of the laws of physics is known to be incomplete. Stating that physical things are absolutely impossible is often considered un-scientific.
Yeah, we know the laws of physics is incomplete because everything is like a jigsaw puzzle. Perpetual motion doesn't fit in our physics model, if it does turn out to be true, it would rewrite everything we know. I wouldn't get your hopes up though, there hasn't been one scientific observance to prove creating something out of nothing (essentially what perpetual motion is) since well, uh, forever.
I'm not saying it's impossible, but if it is possible, it's like opening pandora's box.