I'm surprised you weren't aware of this.
I can understand it, however. Patenting a graphic technique is perhaps foul play? (Imagine if normal-mapping and others were under the same condition).
Stencil-shadows pretty much died because of this and from the fact that they don't scale well with higher-detail meshes, which was the natural prospect for game engines.
But with mobile specs and some lower-end consoles (the Wii, for instance) they can present a reasonable method again.
There are ways around camera intersection of shadow volumes that don't rely on depth-fail to render stencil shadows, but they're more complex and in some cases less accurate.
I'm not a lawyer. I was hoping something as simple as changing the stencil operators would not infringe the patent; After all, it wouldn't follow the description of the patent anymore.
Can anyone shed some light (no pun intended) on this? I'm referring to this post here (Shadow Volume SceneProcessor) where the OP claims at the end of his post of not infringing the patent by using different operators for the stencil function.