Apple followed and in fact integrated OpenGL so deep into MacOS X, that the OpenGL version available is tightly coupled to the version of MacOS X installed. When OpenGL got first released the API somehow found its way into the ABI (Application Binary Interface) contract of Windows, Solaris and Linux (LSB-4 Desktop) in addition to it's origin Sun Irix. This might change in the future, when new GPU programming interface allow to truly implement OpenGL as a library, but for now it's a programming API towards the graphics drivers.

And for the time being, OpenGL implementations are part of the GPU drivers. OpenGL by itself is merely a set of specifications on what commands an implementation must follow. This is not how OpenGL finds the way into computer system. This misconception leads to many questions in the form 'how to I install OpenGL' or 'where to download the OpenGL SDK'. One of the most common misconceptions about OpenGL is, that it were a library that could be installed from 3rd party sources.

Opengl 4.1 library download