Lua scripting manual has been removed, use the Mach4 API help file.
The "Mach4CoreAPI.chm" is located here in your Mach4 install folder:
YourDriveLetter:\Mach4Hobby\Docs\Mach4CoreAPI.chm
The help file is UP TO DATE per release of Mach4, there have been many, many changes since the scripting manual was done, and it is now been depreciated and its thread removed to not cause confusion to new (or existing) users.
Scott