Issue with usbserial for arduino clone
You will need to allow the use of unverified drivers for this version of the Arduino. Unlike the genuine Arduino this board needs the ch340 and ch341 drivers and because they are not verified you will need to run the following command in order for them to work:

sudo nvram boot-args="kext-dev-mode=1"

I just got a handful of these clones (so cheap) and once I installed the drivers and then set the nvram kernel extensions to dev mode all was OK.