Not entirely. As I understand it, that re-licensing occurred when a member of the Doom community emailed John Carmack asking him if he would be willing to release the source under the GPL. He said no problem, but there was never an official source drop with the updated license from Id Software. Carmack's email is all there is, and there's some ambiguity over whether he had the legal right to unilaterally re-license it. This official release puts its GPL status on more solid ground.

When I saw the title I thought they released the source for Doom 3...

Doom 3 source was released more than 10 years ago

https://github.com/id-Software/DOOM-3

As an example of something built with that, you can play Doom 3 in your browser:

https://wasm.continuation-labs.com/d3demo/

Incredible this can run in the browser on my freaking phone! I remember playing Doom 3 when it came out, and my overclocked, water-cooled beast-mode computer at the time in the early 2000s could just barely do it.

Dooms lighting was just next level. I remember realizing I'd need to upgrade from my Radeon 9600 Pro.

Oh thanks! That somehow went past me.

I'll be downloading a native port though.