Hacking: Building/Mac OSX
GIMP has an official build whose scripts are located at this repo: https://gitlab.gnome.org/Infrastructure/gimp-macos-build
To use MacPorts, you first install the MacPortsapp, which gives you the "port" command. Then you use "port" to install an app such as GIMP, using a "portfile".
The first time you install GIMP, it will take a long time, since it first builds many dependencies.
Some older links explain how to build and install GIMP on an Apple computer running the OSX operating system. We are not sure these instructions still work with current GIMP code.