Nikon has taken Sigma seriously and sued them for US$ 116 million and the Tokyo district court ordered Sigma to US$ 14.5 million, for patent infringement case for lenses with VR technology. Here is teh summary of judgement as posted by Nikonrumors site:2002? Shouldn't Canon sue Nikon
Here is the summary of the judgment:
"Nikon obtained the patent related to VR technology in 2002.
Actually Nikon was the first to come up with image stabilization in 1994, in a 38–105 mm f/4-7.8 zoom lens built into the Nikon Zoom 700VR (Zoom-Touch 105 VR) camera.
Canon produced their first Image Stabilized lens (EF 75-300mm f/4-5.6 IS USM) in 1995
I think what Sigma copied was the 2002 "version" of Nikon's VR technology.