Mate,
Thanks for the prompt reply .
Launching from the command line on a mac is also a bother for me. It says Cannot open Display.
Launching in interactive mode is showing a GTK warning
Launching gimp in interactive mode with sudo switch is showing some additional errors.
I have two installs of GIMP on my mac, one downloaded months ago from the gimp website, and the other using macports. Only the official gimp website one works and so i just pointed the plugins from the macport install found at /opt/local/lib to the working GIMP app. I am not aware of how to download the gimp gap filter any other way to use directly with my working GIMP app.
hope that helps.
*EDIT
I did some checking on the net and realised an environment variable DISPLAY was not set in bash_history with a value ':0'.
I have also downloaded the missing script-fu.init file from gitlab dot gnome mentioned in the screenshot above and placed in the scripts folder in /opt/local/lib/gimp/2.0/plug-ins/script-fu.
Now the only error i get while i try different switches is