--- Toby Bartels toby+wikipedia@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)
__________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com