Says the readme:
This is a modernized (as of 2019) fork of Executor, the "original" version of which you can still find upstream at https://github.com/ctm/executor. The home of the "Executor 2000" fork is at https://github.com/autc04/executor.
Why "2000"? Because that's what we used to call the future.
Executor was a commercially available Mac emulator in the 90s - what makes it different from other Mac emulators is that it doesn't need a ROM file or any original Apple software to run; rather, it attempts to re-implement the classic Mac OS APIs, just as WINE does for Windows.
Executor 2000 feature highlights:
Builds and runs on modern 64-bit Linux and macOS (Windows support is planned).
Rootless - emulated windows are part of your desktop.
PowerPC support (well, not many Apps will run, but it's there)
Support for native Mac resource forks (Mac version)
Exchange files with Basilisk & SheepShaver
Lots of code cleanup, according to my own definition of "clean"
included debugger based on cxmon from Basilisk
started a test suite
Removed old, no longer functioning, DOS, NeXT and Windows ports. (Windows still works, though, via Qt and SDL ports.)
I probably broke lots of other things that used to work.