My impression after reading "Masters of Doom" was that Carmack never really wanted to be in the licensing business. The main driver behind id's early licensing pursuits was Romero, and although Carmack went along, he did so without enthusiasm. After Romero got fired, there was no one at id pushing for the studio to do much besides making games. Epic Games, on the other hand, took engine licensing very seriously from the beginning. There is a feeling of "continuity" between iterations of their technology, and this is very important to toolkit licensees, and something that you don't get from id. I've always felt that Tim Sweeney has a lot more business acumen than most people would expect from a programmer.