Fully Customizable User Interface
GIMP comes with a customizable user interface that was designed by a dedicated usability team. There is even a GIMP user interface brainstorming group. GIMP users can send in usability suggestions to the group at any time.
Once you download and install GIMP, it can be viewed in two ways: single and multiple window modes. The following is an example of viewing GIMP in single widow mode:
The GIMP tool kit, also known as GTK+, is used to create the graphical user interface. It’s a cross-platform widget toolkit, meaning it can be used on multiple operating systems. The GIMP tool kit is licensed under the terms of the GNU LGPL (Lesser General Public License) which allows it to be used freely by anyone.
For a tutorial on how to change interface themes in GIMP click here: http://graphicssoft.about.com/od/gimptutorials/ss/Change-Themes_4.htm
For more on the GNU LGPL click here: http://en.wikipedia.org/wiki/GNU_Lesser_General_Public_License