I read that in 2003 Shimano sued SRAM for patent infrigments on their PowerGlide cassettes.
Well, are those patents still in effect in 2014?
Also, does SRAM have any patents on cassettes? And what about chainrings?
As you probably know from reading the newspapers, patent law can be complicated. I suspect there are multiple patents involved in the index-shifting technology, ranging from chain design, shifter design, cassette/chainwheel tooth profiles, etc.
If the 2003 patents have expired, then there are probably successor patents in place but that is just my guess.
As far as your last question about SRAM patents, take a look at a SRAM cassette and/or their documentation and see what patents they cite.... it may give you some of the info you want.
Why do you ask? Knowing what is behind the question may help folks provide the info you need.