There's no meaningful reason to do this other than corporate profits.
Well, that is why people go into business.
I'd be willing to bet... that a competent group of people could implement QB in under a quarter of the lines of code
Agreed. But then the business aspect comes into play: can they market it well enough to displace the market leader? There's plenty of crap out there that makes money despite the fact that better options exist. If it was as easy as just competent programming, someone would have done it already.
Given the dubious rationality of accumulating significant wealth for its own sake
People accumulate vast wealth (and continue to work) as a measure of success.
There's one thing Wikipedia could learn from Facebook...
How to look like a MySpace profile, circa 2006? I'm looking at you, Timeline.
What about open source babies(whatever that means)?
The missionary position is hardly protected by copyright or patent. Unless you choose to make your baby using some proprietary method for fertilzing an egg (artificial incemination? patented sex positions?) I think your baby can be considered open source.
"Life is a garment we continuously alter, but which never seems to fit." -- David McCord