1. Download and install d2xx drivers http://www.ftdichip.com/Drivers/D2XX/MacOSX/D2XX1.0.4.dmg (from http://www.ftdichip.com/Drivers/D2XX.htm)
2. Install OpenOCD from homebrew (http://mxcl.github.com/homebrew/)
$ brew install openocd --enable-ft2232_libftdi