True, the basic knowledge how the NES works, how to emulate it, and how to write games for it is out there, but aside from the real hardcore rom hackers, most people writing code for it probably don't know anything about how the old games were actually developed. They probably have no idea how to make a really efficient DTE system (were those used in the NES, or only the SNES?)
Anyway, it's basically gotten to the same way computers are: nobody but the true hardcore geeks/oldschool programmers know assembly now, and nobody but the real ubernerds who have reverse engineered NES games likely know much about the real innards of most NES game, despite the fact that the basic working knowledge is there.
(Don't fault me on this stuff, it's 3:24, I'm insanely tired, and I've been drinking a bit after work. Also, this keyboard is still sticky :/)