A registration key is only needed at the beginning of the installation for FDC.
FSUIPC is an interface module for add-ons to speak to Flight Simulator.
FDC Live Cockpit installs an unregistered FSUIPC module into Flight Simulator.
You do not have to register this module as it will work perfectly with this and other add-ons.
FSUIPC will only have to be registered if you want enhanced options for your
Flight Simulator and its controls which are not needed by FDC Live Cockpit.
To run FDC Live Cockpit simply click on the FDC icon and it will run.