Open Watcom is an Integrated Development Environment (IDE) for Fortran and C/C++ languages using the Watcom compilers.
"It is a joint effort between SciTech Software Inc, Sybase and the Open Source development community to maintain and enhance the Watcom C/C++ and Fortran cross compilers and tools. An Open Source license from Sybase allows free commercial and non-commercial use of the Open Watcom tools."
To use IUP with Open Watcom you will need to download the "owc1" binaries in the download page.
After unpacking the file in your conputer, you must create a new Project for a "Windowed Executable" and configure your Project Options. In the Project Options there are 2 important places:
comctl32.lib iup.lib iupcontrols.lib cd.lib iupcd.lib im.lib im_process.lib iupgl.lib opengl32.lib glu32.lib