This are simple step-by-step instructions on how to build gimp on Mac OSX. This guide assumes that you are already somewhat familiar with jhbuild. Before you begin, it's best to remove all references to previous jhbuild, MacPorts, or HomeBrew install from your .profile. Simply renaming it would suffice.

The dollar sign precedes terminal commands.

These coomands will check for a .profile in your $HOME directory. If one exists, it will rename it.
$ if [ -f $HOME/.profile ];
$ then
$ mv $HOME/.profile $HOME/.profile-backup
$ fi

For non-Lion users, you will need to install git in order to install jhbuild. You can download a Mac binary from:
http://git-scm.com/

Once you have git set up, you should download and install jhbuild:

$ cd $HOME
$ curl -O http://git.gnome.org/browse/gtk-osx/plain/gtk-osx-build-setup.sh
$ sh gtk-osx-build-setup.sh

Now add the jhbuild path to your shell and new .profile:

$ export PATH=$HOME/.local/bin:$PATH
$ echo 'export PATH=$HOME/.local/bin:$PATH' > $HOME/.profile

In order to properly install gimp on osx you will need to use a preconfigured jhbuildrc provided by gimp:

$ curl -o $HOME/.jhbuildrc-gimp http://git.gnome.org/browse/gimp/plain/build/osx/jhbuildrc-gimp?h=gimp-2-8

Now you can download and install gimp, where 'gimp' is the directory prefix, and '10.6' is the minimum version you are building gimp for. As it stands, you should be able to leave the values as they are.

$ JHB=gimp GIMP_SDK=10.6 jhbuild bootstrap --ignore-system
$ JHB=gimp GIMP_SDK=10.6 jhbuild build gimp-python

This should work. However, in the odd change that, during the compiling of gimp, docbook.make (or the like) is not found, you should copy and paste the configure script and options in the gimp source folder. Note, all you need to do is configure gimp once, then jhbuild will be able to handle gimp by itself.

In order to create a .app you'll need to download an install gtk-mac-bundler.
This will install gtk-mac-bundler into ~/.local/bin.

$ cd $HOME/Source/
$ git clone https://github.com/jralls/gtk-mac-bundler.git
$ cd gtk-mac-bundler/
$ make install

Now create the gimp.app.

$ cd $HOME/gimp/10.6/source/gimp/build/osx
$ gtk-mac-bundler gimp-python.bundle

Please note that this is not a finished process, and there are a few issues that still need to be fixed. Please joing #gimp on irc.gimp.org if you have any questions.

