I am just barely old enough to be familiar with the original ADVENTURE.
The source code to the ORIGINAL version has been found! not the Don Woods enhanced version, which looms large in hacker lore and whose source can be found here and which was the basis of early text-based adventures like Zork on the Apple II, but the earlier version (1975-76) that Will Crowther wrote based on the real-life Colossal Cave in Kentucky. There’s a corresponding scholarly article in a humanities journal (possibly it has moved here) about the source code.
The source code was found in an archived copy of Crowther’s account at stanford AI lab about a year ago.
It is neat to peruse. it’s in Fortran IV, the total source code is 13K with an additional 19K file of text data (game messages, numbers describing the connectivity graph of the areas in the game, etc.) I couldn’t get it to compile using g77, i assume because of syntactic differences between Fortran 77 and Fortran IV.
It’s our heritage as hackers! I think of it as the equivalent of trying to read Chaucer in the original (which, by the way, is another fascinating exercise i recommend if you haven’t tried it).
UPDATE: Someone has ported the code to compile under g77!