I really like the 5th revision and that is open source and I was thinking to help with the development and add/remove features. I have looked everywhere and it seems nobody is talking about modding and flashing their board. Is it because it is that easy and obvious? I will try to build and flash the firmware to an ESP8266 to see how it will work.
Check the home brew category for others that build their own hardware and/or modify the firmware for their use.
GitHub indicates there have been 60 forks of the firmware.
I am more of software guy, so the only thing I need to know is that if I get the 5th revision of the board and I plug it to the usb then I can upload my modified firmware? I am ready to order and I just want to make sure of this.
You can flash the board with ESPTOOL.PY. The ESP8266 is a standard open hardware nodeMCU with an ESP12S. If you can flash a nodeMCU 1.0 you can flash an IoTaWatt.
I would strongly recommend that if you intend to develop your own firmware, you use platformio to control the library dependencies.