Go to:
~/OpenNI2/Drivers/
In my case:
and paste the drivers directly in the SimpleOpenNI folder:
/libraries/SimpleOpenNI/library/osx/OpenNI2/Drivers/libfreenect2-openni2.0.dylib
and /libraries/SimpleOpenNI/library/osx/OpenNI2/Drivers/libfreenect2-openni2.dylib