Given the wealth of text this chapter offers regarding derivative works,
this section really is necessary to give context on this point and
assure that the reader is not unduly swayed to believe that the
derivative work discussion is a central tenant of understanding
copyleft.
Long term, it may make sense to move the entire chapter on derivative
works to a different part of the tutorial. Historically, it was placed
here because when teaching courses on the subject based on this text, I
found as an instructor that questions about derivative works became so
rampant from students during discussions of GPLv2§2 / GPLv3§5 that
derivative works discussion ahead of time was the only way to quell the
onslaught of ultimately off-topic questions.
Thus, the placement of the derivative works section in this location may
in fact be merely an historical artifact that this text was written
originally to accompany an in-course presentation. While I'd still
recommend organizing a classroom presentation of these topics in that
order, I no longer believe the written materials must follow suit.
enyst was quite correct that more explanation was needed here about how
an entity achieves exclusive relicensing rights. However, the details
are somewhat off-point to what the section is trying to explain, so the
details are best placed in a footnote.
I've also separated out copyright assignment from generating all of
one's own copyrights. This may be a distinction without a difference,
but a laundry list seemed appropriate here. Perhaps this should be
shortened in future.
I've long been aware that GPLv2 "technically" governed private
modifications and that generally there were probably more requirements
on privately modified versions of GPLv2'd works than most people assumed
in practice, including commonly held public interpretation by FSF.
HT Wolvereness, who pointed out to me that GPLv3 solved that problem.
When I spoke to Fontana about it, he was indeed aware that this text was
"missing" in GPLv2 and that GPLv3 properly added it, through some
politics during the GPLv3 process.
I've added herein the ultimate historical conclusions about GPLv2's
interpretation and how GPLv3 clarified it. I've left out the color
about the politics of how it got added, not because they are not
interesting, relevant and germane to tutorial, but because we don't have
a good place yet in the tutorial for discussion of GPLv3 drafting
politics, and frankly if we have such a section, Fontana ought to write
it, not me.
This text needs to be clear that GPLv2§2 doesn't govern merely the act
of modification, but distributing modified versions (in whole or in
part). The previous text here wasn't clear on that point.
While both GPLv2 and GPLv3 have long been considered to grant unabridged
right to private modification, GPLv3 has much clearer and explicit
wording to this effect.
This should be noted when that paragraph is explained. This change
herein does that.
HT Wolvereness for pointing this difference between GPLv2 and GPLv3 out
to me.
