The exact command to simply launch a new instance from Mac OSX command line is
/Applications/Godot.app/Contents/MacOS/Godot -e
Note that if you do this, the process will remain active in the terminal. You can pass the -d option to open in the background
/Applications/Godot.app/Contents/MacOS/Godot -e -d
It is possible on your computer that Godot.app lives in /Users/YOUR_USERNAME/Applications rather than root /Applications