Freeglut is a completely open source alternative to the OpenGL Utility
Toolkit (GLUT) library. GLUT was originally written by Mark Kilgard to
support the sample programs in the second edition OpenGL Redbook. Since
then, GLUT has been used in a wide variety of practical applications
because it is simple, universally available, and highly portable.

GLUT (and freeglut) allow the user to create and manage windows
containing OpenGL contexts and also read the mouse, keyboard, and
joystick functions on a wide range of platforms.