This copyright comes from near the beginning of jarg400.info:

Copyright:
This document (the Jargon File) is in the public domain, to be freely
used, shared, and modified.  There are (by intention) no legal
restraints on what you can do with it, but there are traditions about
its proper use to which many hackers are quite strongly attached.
Please extend the courtesy of proper citation when you quote the File,
ideally with a version number, as it will change and grow over time.
(Examples of appropriate citation form: "Jargon File 4.0.0" or "The
on-line hacker Jargon File, version 4.0.0, 24 JUL 1996".)