A lot of the code is automatically generated. The following are generated based on specs/gl.spec and specs/enum.spec (from OpenGL.org): apple_xgl_api.h apple_xgl_api.c exports.list include/GL/gl.h include/GL/glext.h (includes the OpenGL framework glext.h) The gen_code.tcl script is what executes the various gen_*.tcl scripts to produce those. You will need Tcl 8.5 for the gen_code.tcl script. The tests/ directory contains some tests that are built in testbuilds. The tests built in testbuilds don't require installation of the library.