Warp3D Nova offers no backwards compatibility, just as OpenGL ES2 is not compatible with OpenGL ES1, thus mobile drivers implement both. I don't think Mesa was even considered, otherwise they would have gone straight for a Gallium3D driver, which would have worked with Mesa out of the box. IMHO that would have made more sense, since it'd have offered backwards compatibility with old software with a nice speedup, plus the new shader-based OpenGL APIs. Best of both worlds.
Since neither Warp3D Nova, nor the planned OpenGL ES2 wrapper implements the fixed function pipeline, old software can only use it, if someone provides a full OpenGL implementation. This can be Mesa, Regal, or whatever else there's out there.