It’s the ‘classic’ MacOS. And it requires Code Warrior 10 to build. Apparently its for the PowerPC only, although I haven’t tried to compile it yet, as I foolishly just upgraded to 10.5 on my PowerPC, which of course has no classic support.
It’s a nice present from Night Dive studios. I know that many people are mad at their reboot being consumed by feature bloat, but at least they aren’t going down into obscurity.
As always, enjoy!