Implementation of OpenGL(only a part) in pure C#.
Games, 3D Modeling, Visualization, ...
glut, gl.h and Graphics Card Driver works together. CSharpGL.Windows, CSharpGL and Graphics Card Driver works together. SoftGL.Windows, CSharpGL and SoftGL works together. They initialize OpenGL's Render Context and Canvas etc on different OS platforms.
gl.h is declaration of OpenGL API in C. CSharpGL is definition of OpenGL in C#. They describe the same thing deep inside. They define what OpenGL has in a blueprint.
Implementations of OpenGL API in hardware or software. The Render Context object(or struct) is created here.