Do you really think a commercial publisher is going to release their back catalogue and current works for free?
Nope. Though I think technically that is going much further than what I was asking for. I merely meant the core systems and mechanical terminology, not the literal length and breadth of every possible concept and story. So, for example, if I wanted to write an RPG that used the terms "Paragon Path" and "Epic Destiny," that would be permitted, but having an ancient war between the dragonborn kingdom of Arkhosia and the tiefling kingdom of Bael Turath would probably not be permitted.
Even with that qualification, however, your core point remains correct. I find my proposal almost totally unbelievable, in fact. If WotC made every past edition's core mechanics open game content, I would be genuinely and thoroughly shocked.
Because at this point, I'm going to
need to be genuinely and thoroughly shocked if WotC wants to earn forgiveness quickly and fully. There may be other, longer roads to forgiveness, but this would be the fast and dramatic one, a show of unequivocal good faith.
My
expectation is that WotC will dig themselves deeper for the next six months to a year, and when they
finally realize that they are making things even worse, they will fumble for another six months to a year making half-arsed, half-hearted, insincere, hollow gestures and platitudes toward doing better and changing their ways. When these efforts don't pay off either, there will be a period of silence as the new corporate leadership will be pressured to resign and given a golden parachute. Then new leadership will come in, at which point it becomes difficult to predict how things will advance from there. By that point, ORC will almost certainly be complete and will have galvanized the 3PP scene, and WotC/Hasbro will be wary of the optics of a nasty fight in the courts (if they didn't jump on such a suit immediately, that is, back during the "dig themselves deeper" phase.)