yep, I agree with you. The product description seems quite ok
a screenshot from their website
and it says:
"VGA2USB software is compatible with DirectShow on Windows and QuickTime on Mac OS X, which allows third-party applications to use VGA2USB as a video input."
Of course it seems impossible for $300 to get something like this working properly compared to the pro products, but if we can have users feedback about it I'd be very happy to know if we're wrong or not