Different planes, different ADIRUs:
I agree with the point however my understanding is that it is the same software!
If one ADIRU comes from Honeywell and the other comes from Litton (or whoever bought them out) you can pretty much bet the eternal salvation of your soul they don't use the same software.
Much patent-infringement and unfair-restraint-of-trade litigation has transpired over the years between those two companies and their respective RLG products.