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.
It features a hard-wired Windows 95-style theme available for both Microsoft Windows itself as well as the X Window System (which is used on many UNIX and UNIX-like operating systems).
The FOX toolkit has been released under the GNU Lesser General Public Licence. Development began 1997 by Jeroen van der Zijp while he was affiliated at CFDRC. Since then, Jeroen van der Zijp maintains the core library and test applications, with the help of a growing user community.
The FOX toolkit is written in C++, with language bindings available for Python, Ruby and Eiffel. The FOX source code distribution supports building with many different (commercial and free) C++ compilers.