Mesa is a 3-D graphics software library that mirrors OpenGL's API closely.
It's worth pointing out that the library should not be referred to as MesaGL for legal reasons. Simply refer to it as Mesa or The Mesa 3-D graphics library. Overall, Mesa seems to be a useful and reliable software for those seeking a 3-D graphics library with an OpenGL-like API.
Version 7.5.2 / 7.6: N/A