The project you linked to uses a feature of the atmega to speed up the a/d sample rate, leaving little processing for other work. It also sends a 512 byte payload, whih is nice for graphing, but Im guessing you'd like a count of lightning, strength, and distance. This one would give strength and count. If I were doing this, I'd use 2 arduinos, 1 as a detector, 1 to parse the data and act as the mysensors node. Look through the apu docs. There is probably a reasonable data type to send the processed data to domoticz or what ever you like.
If I were really doing this, I would look for a more robust detector using discrete components. And connect it to an arduino/mysensors node.
This one may work. (Maybe more complicated to build)
http://www.techlib.com/electronics/lightningnew.htm
An old am radio tuned to an unused frequency, could be connected to an arduino analog pin with some resistors and capacitors, and sampled at 9600 samples/sec or less and could be done with 1 arduino.
