Just two years ago Apple released it under a very strict non-commercial use "be careful how you look at this" license, to the CHM:

https://computerhistory.org/press-releases/chm-makes-apple-l...

I briefly looked at it, it's a pile of Object Pascal and M68k asssembly. I haven't looked to see if anybody has managed to make it compile in any kind of available-today compiler yet.