Compiling the source
How to compile and flash arduino code is documented many times on the web.
A good entry point for how to start with arduino and to compile the code is here: http://arduino.cc/en/Guide/HomePage
A good entry point for how to flash the code is here: http://code.google.com/p/arducam-osd/wiki/Cfg_Update_Firmware
But don't use their hex file of course, but compile the right one for minOPOSD.
The code is here:
http://code.google.com/p/minoposd/source/checkout
And use the 'OSD Config Tool' from my code section trunk/Tools.
Take the libs from one of the two other original projects http://code.google.com/p/arducam-osd/ and http://code.google.com/p/minimosd-extra/ .
The main add-ons to the original code can be found in the files:
UAVTalk.h
UAVTalk.ino
FlightBatt.h
FlightBatt.ino
PacketRxOk.h
PacketRxOk.ino
AnalogRssi.h
AnalogRssi.ino