i dont know about installing on a NAS but here is what i did;

I took the files provided by Jeroen Zeist in the first post. ps. thanks Jeroen!
"Intergas Incomfort Lan2RF control 1.1.zip"

copied them;
script_time_intergasincomfort.lua
script_device_intergasincomfort.lua

to /home/pi/domoticz/scripts ...

Ok, my firmware of the gateway is IC3-1-ICN-V1.17. With this version it is required to give the login details. If I access the gateway like:
http://user:password@ipaddress_gateway/protect/data.json?heater=0

But I am not a coder but I am willing to try. But where to begin? Anybody who can help ...