Yes, this is all what I was trying to say when I posted yesterday, and it wasn't intended as a thread derailment. The listed "counterexamples" (the useful ones that weren't vacuous thinly-veiled flaming) are still developed by a smaller core group. Check out the dev pages, every listed dev team is under 10 people, with a few more that come and go over time that still have their names stamped on the page as an honorary.
The long lists of contributors are all relatively minor, such as localizations or installer graphics, idea consultation, and what have you. There's no grand unified project that has dozens of people all working as a team to fix things, like proponents of open-sourcing DF think will happen. Those kinds of projects are run by software companies that have coders on payroll, because it's much easier to accomplish something when you can fire someone for not agreeing with you about how it should work.
Really, releasing the source for DF would lead to exactly the situation stated above, dozens or hundreds of different solutions, flavors, releases, tweaks, whatever... with none of them working together and diluting Today's established formula. We're left where we started, with Toady being the one that has to fix his bugs (or not, it's his creation).