[TomasSedovic]

I haven't the faintest idea, which is why I asked aphextron. Indeed, until today I thought the Unreal Engine was FOSS, but seems to be just source-available. That said, didn't id Software / John Carmack release a bunch of engines under FLOSS licenses in the past?

There are many more or less serious potential explanations: not enough people care, it wasn't (or still isn't) financially feasible, the people able to develop AAA engines are actively against sharing source or ideas, there's an engine development cartel actively pushing against it to keep their revenue.

Or it might just be a social or historical accident -- we may just have been extremely lucky with Linux and projects on that scale will never come again.

Or maybe everyone thought it would be a great idea but they also thought it would never work and so no one seriously ever started an open source engine. Maybe Godot will be a true AAA engine that will surpass them all in a few years.

I don't know.

[dkersten]

id Software released their old deprecated engines as open source, when they had new engines they were pushing instead. It was a nice friendly gesture, but the engines typically weren’t competing anymore.