--- Toby Bartels <toby+wikipedia(a)math.ucr.edu> wrote:
But this is precisely the comparison that is relevant!
The public domain, like CC-by, is free but not copyleft.
And the public domain ''is'' made use of for derivative works
more readily than copyleft material is.
Copyleft for content has existed for a very small part of the history of
copyright, so I wouldn't expect anything else at this point. The volume of PD
content vs copyleft content also does not compare (lots more PD but most of it
isn't very good).
My point about positive feedback is still valid here - each of those
proprietary derivative works are forks that for practical reasons can never be
combined to create something better. Effort is wasted making the same
improvements in many different ways when that effort ''could'' have been
condensed and combined into a smaller set of forks that could exchange bits and
pieces back and forth as needed. The time saved could be used to write more
content or further improve the wording of the old.
Proprietary forks dilute effort permanently while improvements to copyleft
forks can be backported to the original - or any other copyleft fork for that
matter. Thus copyleft encourages the freer exchange of knowledge (PD and
attribution-only licenses encourage the exchange in just one direction).
-- Daniel Mayer (aka mav)
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