The GIMP download page says:
Homebrew is similar to Macports and provides packages (aka formulas) to
> install, either by compiling them from source or by using pre-made
> binaries. While there appears to be no formula for GIMP itself, there are
> reports that all dependencies are available. This may help to build GIMP
> from source.
There is an add-on to Homebrew called Homebrew Cask that is designed to
work like Homebrew, but for ".app" installations. The website is
http://caskroom.io/. There is a Brew Cask formula for GIMP.
gimp-web-list mailing list