Earlier quoted context omitted.
I think Microsoft might be willing to release the Infocom build tools and engines under an MIT license – by now they would be of purely historical interest, similar to open-sourcing MS-DOS 1.0 and 2.0. I'm not sure if they'd be willing to do so for the game assets (the room/item descriptions/etc) – it would remove one of the main legal barriers to a competitor creating their own game set in the Zork universe. The For…
We already have build tools for infocom against the Z-Machine, and interpreters themselves since the 90's. Having a public domain or MIT licensed Dungeon/Zork would allow to fix bugs and not worrying about licenses on any Linux/BSD distro.
The TOPS-20 versions of ZILCH (and ZAP) don't seem to be available.
The ITS version of ZILCH from MIT has been recovered, but (from what I understand) it is an earlier version, and the TOPS-20 version which Infocom used later isn't publicly available, and that later version had added features.
In any case, its copyright status is murky, Microsoft could clean up that murkiness.