Basically for anyone else that is kinda confused when you pass light threw something like glass for some reason light splits into two waves, one on each side of the glass, however on the entering side of the glass "backwards/negitive" light is rebounded back to cancel out the first wave of light. So this rebounding wave is what they call backwards light.

It seems pretty far fetched to me personally. Something tells me this MAY turn out to be a hoax in the end.