1) It's a replacement for the original v1.0 obge.dll and should not be installed at the same time. By using the same name "there can be only one!"
2) OBMM includes an install script function "GraphicsixtenderPresent" that looks for obge.dll. This function fails to detect OBGEv2.dll, and thus OMODs that use this function can refuse to install if OBGEv2 is installed. I cannot foresee OBMM getting updated so that this function also looks for OBGEv2.dll
I'm going to start advising people that want to use http://www.tesnexus.com/downloads/file.php?id=21424 to rename the dll so that the OMOD install script can correctly detect that a suitable version of OBGE has been installed...