The technique used in this library is completely different from that needed to decode a signal encoded using the Futaba PCM protocol. That protocol uses proprietary serial encoding and would required much more processing than the PPM decoding used here.
In my opinion it would not be worth the effort to do this – of course you are welcome to take it on if you are up for the challenge. But I would think in most situations there would be no benefit and for those cases with strong interference you would be better of using 2.4ghz technology.
What was the reason you were interested in PCM?