This file comes from the IF Archive, where its description is:
"FORTRAN-IV source code of 501 points version of Colossal Cave by David Long, version 5.2/2, October 1979."
It was uploaded on 1992-12-21.

The spider and "shamut" (not to mention the accompanying README
from Bill Randle) identify it as ANON0501, not a pure copy of LONG0501.

The in-game "History of Adventure" contains David Long's
announcement of a forthcoming "Adventure 6". I've copied
the "History of Adventure" into ./advehist.txt.