While waiting for issue #1 to be fixed so I can actually try it out, I looked at the berryCam.py code.
I notice that you are using defaults for the timeout and preview. This means that the stock raspistill waits 5 seconds before returning with a picture, and in the meantime it is displaying a preview on the HDMI screen attached ot the Raspberry Pi. (Or so I believe, I am running headless.)
If you add the flags:
-t 500 -n then it should return in half a second (which gives it enough time to make a few pictures for exposure time adjustment) and spend any resources on displaying the preview.