The HomeBrewIR driver talks to a LIRC-driven remote (see http://www.lirc.org). Setup is a little different than the regular input devices, because it must be started manually. To set it up, follow these steps:
Follow the directions that came with lirc. You're going to want to configure the 'ircat' program to print strings when you press buttons. Name the strings appropriately, according to what the buttons do. You can do this and test without cajun; you should just get ircat to print the strings on your screen.
Add the HomeBrewIR driver in. I don't think there's any options you need for the driver. Add each keyStroke in as the name of the key you're having ircat print, and map them to appropriate actions in the actionMap as you would any other device.
You'll notice that the 'start driver at boot' check isn't on for the HomeBrewIR; this means that you must configure it to start at boot, a few seconds after cajun boots. do it like this, in /etc/rc.d/rc.local:
/usr/share/cajun & (sleep 4; ircat [lirc-paramters] | /usr/share/cajun/bin/device _devId XXX basedir /usr/share/cajun dbname cajun ) &
where 'XXX' is the device Id for the HomeBrewIR in the cajun device settings screen (where you added the HomeBrewIR in the first place).
That's it... fire up cajun and enjoy your new remote control.