This exists now. Which is to say, it existed before, and the fact that it still does is a friggin' miracle.
It's a code dump of the original ZZT source code circa 3.0 (1991). Some portions were redacted, as they are suspected to be from a third-party (as in, not Tim Sweeney himself), but most of it is there, and anyone who's inclined to give it a look, or to study it against the hand-built, fan-built Reconstruction of ZZT (a recreation of the 3.2 source code) can do that now.