Well, sculpt tool was a seperate program before Blender ate it. I honestly don’t know how much of sculpt tool’s code had to be rewritten for Blender integration. I’m inferring that it was easier to incorporate the existing tool than to copy from it, but I don’t know that’s the case.
I’d think it would be easier to integrate GIMP since only 2D data needs to be exchanged between Blender and GIMP. It seems like the biggest job would be scraping off GIMP’s GUI and putting Blender’s on. And getting the UV stuff to work in GIMP.
If any dev types are interested in this, I can work on the useability and GUI graphics side.
I’m planning to release a 70% finished version of the Extinction Level Event trailer in the next few weeks. I think the project will start to get high profile after that. I’d love to be able to ditch windows and Pshop and do everything in Linux with Open Source tools. If we can get that ability into Blender, I can showcase it to good effect.