Subject: Another dumb GPL question
From: "Stephen J. Turnbull" <turnbull@sk.tsukuba.ac.jp>
Date: Wed, 6 Jun 2001 15:08:50 +0900

>>>>> "Al" == Al Davis <aldavis@ieee.org> writes:

    Al> The question ....  At what point does GPL no longer apply?

    Al> I am not considering doing this.  I want the answer to be "GPL
    Al> always applies", but have some concern that it doesn't.

It always applies.  The whole is always GPL.  It's not a question of
whether program A(n) contains common code with GPL program A(0).  It's
a question of whether program B contains _any_ common code with GPL
program A.  If so, then program B "is GPL" (the quotes mean that I
understand the legal distinction between the copyright and the license
to redistribute, OK?)  So the principle of mathematical induction may
be applied.  A(0) "is GPL", and A(i+1) shares code with A(i) implies
A(i+1) "is GPL" for all i.  A(n) "is GPL" for all n.  QED.

Note: no hypothesis is made or needed about shared code for n and n+m,
m > 1.

Lawyers may not be mathematicians, but _judges_ must grok mathematical
induction.  That's what we mean by "common-law legal system".

>>>>> "Rich" == Rich Morin <rdm@cfcl.com> writes:

    Rich> Well, this is a rather similar situation to what happened
    Rich> with Unix 32V and the BSD distribution.  It took a lawsuit
    Rich> to bring everyone to the table, but in the end, BSD was
    Rich> freed.

Only physically similar.  Legally, it's very different in that the GPL
explicitly states under what conditions you may redistribute the code.
This establishes the "inductive hypothesis" without question in my
mind.  The inductive hypothesis, if any, for the Unix -> BSD case is
implicit, and evidently the court decided that it didn't cover the facts.


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