"This collection is meant for education, discussion, and historical work, allowing researchers and students to study how code was made for these interactive fiction games and how the system dealt with input and processing. It is not considered to be under an open license."
This github repo has been up for some years now (this old blog post has some back story: https://blog.zarfhome.com/2019/04/all-of-infocoms-game-sourc... ) -- AFAIK it's the source contents from an old hard drive image from back when Infocom was a company.
(I only checked hitchhikers and starcross, because github is giving a lot of error pages for these right now.)