That had the ring of truth to me, and I've done a significant amount of porting to IBM z/OS and IBM System i (each of which have a lot higher 'weirdness' quotie

That had the ring of truth to me, and I've done a significant amount of porting to IBM z/OS and IBM System i (each of which have a lot higher 'weirdness' quotient than NT --> Unix. If there is a compiler on the platform for the language in which the product is authored, getting core functionality standing up and walking can often be accomplished in a shockingly short timeframe. Getting things to run well, properly documented, interfacing as desired with other components on the system, and effectively marketed to a different audience...much harder and time/resource intensive.