My guess is that this adapter uses FTDI chip. So you can download the drivers and then simply write and read data the same way you would with a regular serial port. The device name will be something like /dev/cu.usbserial-3E1
Just get any reference for OBD codes and then it is really easy to write your own software to get whatever data you need.
Lawicel has Linux drivers. No idea if they work with the Mac OSX. Tomorrow i'll know more.
1. Linux driver won't work. The architecture of both systems is much different.
2. As you can see on the attached image taken from canusb.com site, Lawicel DOES USE FTDI chip to convert RS232 (output from the CAN controller). So it WILL appear as a normal serial device under OS X when you download the generic FTDI drivers for USB-RS232 adapters/chips. Just download the bloody drivers from http://www.ftdichip.com/. After that it is plain and simple write/read on a serial device.