Carmack rewriting Doom 3 source code to dodge legal issues | VG247
http://www.vg247.com/2011/11/17/carmack-rewriting-doom-3-source-code-to-askew-legal-issues
According to a tweet from the developer, Bethesda’s lawyers are “skittish about the patent issue” surrounding the code for “Carmack’s Reverse,” which is a stencil shadowing technique patented by Creative Labs and jointly created by the id legend and other coders.