[user____name]

FTE barely qualifies as a pure Quake engine at this point though, it does tons of stuff.

[vkazanov]

It does a lot, yes, but also is very much a continuation of the original codebase - i've spent quite some time tinkering with internals of it.

[jsheard]

Yeah, but Half Life 2's Source engine was itself a continuation of Goldsrc which was itself a continuation of the Quake 1 engine. The lineage is there but beyond a certain point it's not really Quake anymore.

GZDoom/UZDoom is a similar grey area, it is built on the original Doom codebase but they've added so many features that it's practically its own distinct engine now. Those forks can even render arbitrary 3D models, which OG idTech couldn't do until Quake.