Gamasutra quotes id Software's John Carmack and Tim Willits talking about their happiness at no longer being in the engine licensing business since being purchased by Zenimax. According to Carmack, this is not a business he ever was fond of in the first place:

"It's interesting when you look at our technology licensing -- it was never really a business that I wanted to be in," he said. "In the very early days, people would pester us, and we'd just throw out some ridiculous terms, and we were surprised when people started taking us up on it."

"I didn't want to be in the process of supporting a lot of outside teams, because you feel beholden to not make radical changes when it's going to pull the rug out from lots of other people," he explained. "When it's your own team, you can make the sensible decision that [a big change] is going to be worth it, that it's going to suck for a while, but we make our way through it. But you don't want to do that to other people."