Regarding custom chips: Given progress in microcontrollers, I can't see why their function cannot be emulated in a $5 arm64 processor. What's left is the details of the electrical interface to the powerline and the RF protocol, and then the logic of the Insteon network. How hard can it be to develop an open-source design to replace the PLM? Just minimal connectivity to each of the linked devices would allow your home automation controller (eg ISY) to run the network. Who owns the intellectual property?