More information of this firmware server and its content, please take a look at: ArduPilot pre-build binaries guide

How to build ardupilot to support Remote ID? More read here, here

git clone --recurse-submodules https://github.com/ArduPilot/ardupilot.git
cd ardupilot
./waf configure --board  FMUV3 --enable-opendroneid   #FMUV3 is your board, you can change other
./waf copter

Firmware : /PIXHAWK6C