Implementations
The original GLUT library by Mark Kilgard supports the X Window System (GLX) and was ported to Microsoft Windows (WGL) by Nate Robins. Additionally, Mac OS X ships with a GLUT framework that supports its own NSGL/CGL.
Kilgard's GLUT library is no longer maintained, and its license did not permit the redistribution of modified versions of the library. This spurred the need for free software or open source reimplementations of the API from scratch. The first such library was freeglut, which aims to be a reasonably close reproduction, though introducing a small number of new functions to deal with GLUT's limitations. OpenGLUT, a fork of freeglut, adds a number of new features to the original API, but work on it ceased in May 2005.
Read more about this topic: OpenGL Utility Toolkit