I just saw a posting about Adaptable Gimp that looks very intriguing. It is Gimp with an extra piece added to the interface. This gives it the ability to step the user through common tasks by entering a search term like "crop a photo" and getting back the list of tools needed to perform it, in order, with commentary. These "task sets" can be edited and added to online at the adaptable gimp website.
It is licensed the same as Gimp, under the GPL. See the faq page: http://www.adaptablegimp.org/w/FAQ
Here's the url: http://www.adaptablegimp.org/w/Welcome_to_AdaptableGIMP for the home page. It's set up as a wiki.