I would like to know about the main specs about this layer that renders OpenGL through software emulation.
What are the supported extensions and what is the OpenGL version supported? Fixed or programmable pipeline?
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Going by the header file (mine is in C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Include\gl) it's OpenGL 1.1 with the GL_EXT_vertex_array, GL_EXT_bgra, GL_EXT_paletted_texture, GL_WIN_swap_hint and GL_WIN_draw_range_elements extensions. That means fixed pipeline only and lot of modern functionality you might take for granted missing.
I'd strongly advise that you not even think of using this. It's a pure software implementation, and not a very good one at that - see: http://www.azillionmonkeys.com/windoze/OpenGLvsDirect3D.html, search for "CosmoGL" - so you can expect performance in the order of less than 1 fps. Yes, that's less than one frame per second (your graphics hardware plays a far more prominent role than some people seem to think).
If you really must use a software implementation Mesa 3D may be a better option: http://www.mesa3d.org/. As a software implementation it's still going to give you low-single-digit framerates, but at least you'll get support for more modern features (up to GL3.0 with more recent releases).