David Long began writing what was then called "Adventure 5" while a grad student at the University of Chicago in 1979. The version playable here extends Crowther and Woods' original game from 15 treasures to 30, and from approximately 130 rooms to approximately 250.
Long's game engine was a strict extension of Crowther and Woods' original Fortran code, and continued Woods' practice of writing maintainable, copiously commented source code. However, Long wrote a new English-language parser, explicitly influenced by "an excellent rival game to Adventure, called DUNGEON, developed at M.I.T." — the game that eventually became Infocom's famed "Zork" series. Unlike Crowther's simple two-word parser, Long's parser could deal with complex commands such as "get brass lamp and put lamp and axe in leather sack."
Long released several updates to the game, including a lost 751-point version circa 1980, but this particular version's ancestry diverges before then. Starting from a 501-point version, Doug McDonald added some puzzles (including nine rooms and two treasures), ported the entire game from Fortran IV to Fortran 77, and posted it to Usenet in August 1990.
This particular version of "Adventure 6" was written by Arthur O'Dwyer in C, following McDonald's Fortran version. Certain spelling errors and many programming bugs in the original have been fixed, and a single Easter egg added, but the intent is to be basically faithful to the intended behavior of the original game.