FOX differentiates itself in the following way from other cross-platform toolkits:
Tk is a cross-platform toolkit but does not have all of the widgets that FOX considers desirable.
Qt had a different licensing model, which might have required a commercial license in some cases where FOX would not. (This is no longer the case starting with Qt 4.5.)
wxWidgets promotes the use of native widgets on each supported platform.
FLTK is a fast, low-footprint library that supports rapid application development, and requires less code to use, but lacks advanced widgets.
All of these toolkits have some support for programming natively on Mac OS and/or Mac OS X platforms, which FOX currently does not support[
The FOX toolkit is an open source, cross-platform widget toolkit, that is, a library of basic elements for building a graphical user interface (GUI). FOX stands for Free Objects for X.