IUP is a multi-platform toolkit for building graphical user interfaces. It was developed at Tecgraf by means of the partnership with PETROBRAS/CENPES. It offers APIs in three basic languages: C, Lua and LED.
The iup-porting is a maintenance project to make IUP a little bit easier to integrate into other project. It also hosts some test snippets. I simply downloaded the IUP release package, made my own patches, built and tested some functions, then commit here.
The IUP details can be found at http://webserver2.tecgraf.puc-rio.br/iup/
The downloadable packages of IUP can be found at https://sourceforge.net/projects/iup/files/
In this page https://sourceforge.net/projects/iup/ you may find the IUP is MIT License so iup-porting is set to MIT too.