It was my task to create a program which is able to analyse data in some way. The user of this program does not necessarily need to have programming skills in mathematica. The only task for him/her is to start mathematica press evaluate notebook and be able to use the program correctly by pressing buttons or providing parameters. The program is an autonomous pop-up window with graphical user interface.
The GUIKit is only a package in Mathematica enabling the commands to create own windows, widgets and scripts. The complete program is written in Mathematica. The pop-up window is called by the command GUIRun[...].
Thank you for your ideas.