FreeGameDev

Yep. This should need no introduction

https://github.com/nightdivestudios/shockmac

My understanding is that this is the more or less failed reboot and it was leaked. The code probably uses either the unreal or unity engine. (the reboot started with the former but moved to the latter which is a big reason for the failure.)

So I'm not sure if it is actually GPLed.

Note: I haven't done any research just skimmed some HN comments about this same thing. Also saw a video before that covering the history of the reboot.

No, this is the 1994 PowerMac release's source. It is an official GPLv3 code release. Following one of the original Shock developers clued me into it at the earliest so it is legit.

So I guess it did need an introduction

Huh, ok good to know! The people over at HN comments section are very confused then. :3