id boss Todd Hollenshead told Eurogamer at QuakeCon last night that the developer won't be out-sourcing Tech 5.
The news broke as technical director John Carmack was giving his annual keynote to the event.
In the past, id's released versions of id Tech to third-party devs and publishers as middleware, like old rival Epic's Unreal Engine or Crytek's CryEngine.
But Hollenshead said id Tech 5 will only be used within Bethesda studios.
"It's going to be used within Zenimax, so we're not going to license it to external parties," he said.
"It's like, look, this is a competitive advantage and we want to keep it within games we publish - not necessarily exclusively to id or id titles, but if you're going to make a game with id Tech 5 then it needs to be published by Bethesda, which I think is a fair thing."
He added the only way to work with id Tech 5 as a third-party would be to have your game published by Bethesda.
End of an era, eh?