I'm not one of the developers (I do my best to help with testing), but knowing the development approach, it's probably not feasible to create the firmware for other radios unless they are very close exact hardware clones.
Some of the large scale integrated circuits in the GD77 radio (like the radio chip itself) are not documented, so the developers must do their best to reverse engineer the behavior and operation of the chip experimentally. By trial and error, eventually they are learning the details of how the chips work.
If the other radio models are exact or very close hardware clones it might become possible to adopt the firmware and CPS software, but that is a project in itself, probably requiring more developers to take on the task.
I am amazed and thankful for the level of skill, expertise, dedication to work and enthusiasm that has brought OpenGD77 this far this fast. I worked in software development (I'm a founder of Eclipse) for 31 years, and have rarely seen such an amazing team.
The original GD-55 was not a two timeslot radio. Apparently there is a "plus" version that is.
This table has a capability overview:
https://radiosification.blogspot.com/20 ... adios.html
There is some discussion of firmware here, and while I cannot find a description of the chipset used in the GD-55 or GD-55+, my guess is that they have different chipsets, and not the same ones as the GD-77.
The TYT MD-UV380 and the MD-9600 both use the same HR C-6000 baseband radio chipset as the GD-77:
https://hvdnnotebook.blogspot.com/2018/ ... art-2.html
That makes the task more testing and adjusting to any differences in implementation within the radios and less one of complete reverse engineering.
If your interest is in deploying a higher power hotspot, know that the internal heat dissipation of the radios is probably not designed for continuous transmission. In fact, there is little in the way of heat management, instead relying on the circuit board, case and battery to do the job. I'm still trying to determine if the development lab has ever tested these radios in a continuous duty environment. Until then, I'm limiting my OpenGD77 hotspot to 1 watt power.
Marc