First download “Homebrew” – the package manager/builder for OSX and install it.
curl -fsSkL raw.github.com/mxcl/homebrew/go | ruby
in a terminal window
the make “cup-programmer” by keying the following into the terminal window
brew dfu-programmer
Plug the CUL device into a USB port while holding in the reset button,
Then run
dfu-programmer atmega32u4 erase
dfu-programmer atmega32u4 flash CUL_V3.hex
dfu-programmer atmega32u4 reset
from a terminal window
Unplug the CUL and plug it in again – the LED should start flashing.
Btw. CUL_V3.hex needs to be downloaded from “http://www.busware.de/tiki-index.php?page=CUL”