Gimpshop 2.8 is available for most operating systems, imcluding Windows, Mac OS X, Linux and Solaris.
For Developers: Download GIMPshop 2.8 Source Code: Download Source Code
In Mac OS 10.5 and earlier, you will also need X11 or XDarwin in order to launch and run Gimpshop. We recommend you download and install Apple’s X11
Linux / Debian / Solaris
Linux: Very detailed instructions by Suramya Tomar for compiling and installing GIMPshop under Linux. Suramya.com:
Debian: Download the GIMPshop 2.2.11 for Debian Here