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 Fortran 77 version of Zork has long been available under a "non-commercial use only" license, so they might be willing to release the game assets under such a license too (or maybe a more modern equivalent such as CC-BY-NC or CC-BY-NC-SA)
> We already have build tools for infocom against the Z-Machine
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.
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 Fortran 77 version of Zork has long been available under a "non-commercial use only" license, so they might be willing to release the game assets under such a license too (or maybe a more modern equivalent such as CC-BY-NC or CC-BY-NC-SA)