GIMPShop is a free Open Source image editor that is similar to the popular Adobe Photoshop. Specifically GIMPShop is a version of the GIMP that has been edited to be more user-friendly for Photoshop users.

GIMPShop was created by Attack of the Show's Scott Moschella. The menu structure and terminology are adapted to to look and feel more like Photoshop, and other adjustments were made to make the GIMP more usable. In the Windows version, the Deweirdifyer Plugin has been used to place all of the various windows into one nesting window, so it will act more like a single program that multiple little programs.. Also the menu structure and terminology are adapted to to look and feel more like Photoshop.

GIMPShop was orginally developed for Mac OS X, but has been ported to Windows, Linux, and Solaris.

http://www.gimpshop.net/