I'll be blunt here: taking off my corporate job hat and putting back on my old consulting hat, I'd say it simply: you'll get ~ 90% of the C++ user base support from my open source code for free. If you want more for your niche technology Y, my rates start at $200/hour.
I misphrased myself here: nothing in this statement should be taken as meaning that I am available for consulting work at any hourly rate since I began employment at BlackBerry, and my consulting firm is indeed closed for new business with no prospect of reopening in the immediate future. I meant my original statement in the sense that wanting compatibility with some technology Y is something which can't be expected for free in open source. That includes legacy compilers. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.