There's a patent on it, but it looks like it's ok.
Centrifugal control assembly for camshaft advance and retardation and suppression of cyclical vibration - Patent 5609127
Going by the pictures, that cam gear is huge. I suspect there's only enough gear space on single overhead cam belt driven engines for a mechanism like that. Chain driven cam gears are much narrower, and belt driven dohc gears are smaller. To make a smaller version, the weights would have to be made out of a heaver metal which could drive the cost up too much. Lifespan of the springs might be a problem too.
Also, it only provides 7 degrees of variation. Modern active cam timing has 35-40 degrees.