Yes. Those are old engines, not current-gen tech. They make money off current-gen tech until open-sourcing it makes more sense to them from a financial perspective. This is distinctly different from what CodeCombat has done, which is to open-source their current-gen tech. There aren't going to be any financial consequences (or any other kind), because it's a good idea and there's no reason not to open source. I'm just saying they're the first non-indie Gamedev company to do so (as far as I know) and they deserve all the credit for it.

They only open-sourced them once their value to Id was approximately zero.

It's still a really cool thing to do, but neither Id (or any other game company I'm aware of, anywhere, ever), has released their game as GPL while they were still making significant amounts of money from it (which in practice means within the first couple of months, for almost all games).