Quote:...snip...a GIMP plug-in and must be run by GIMP to be used...
Is this when you start Gimp ? Certainly come across that before but only when the user is trying to run the Gimp plugin ("file-jpeg") on its own in a terminal. Plugins run from within Gimp.
Do you get the message using Gimp and File -> Open ?
I do not use MacOS, if you can give more details the better.