From the author:
The main reason for deleting the project is that new OpenTherm specifications are coming out with different voltages etc. and this PCB has not been tested with them. As such, someone making or purchasing the PCB may run the risk of damaging their boiler and I do not currently live somewhere where I can play around with making new circuits in line with these new protocol standards. Of course, if I ever get the opportunity to develop a new circuit and create a PCB, I would be happy to make a new project for it.