Re: libpng license 2.0

There have been many contributors to libpng, and any of them which 
made a significant contribution are copyright holders with the 
expectation that their contribution is under the license which was 
current at the time the contribution was made.

Regardless of a modified license statement, the previously existing 
licenses are perpetually still in effect unless all the significant 
contributors agree to the new license.  Usage of the software then 
needs to comply with both the old and new license statements.

It would be nice if the libpng license and copyright notices were 
cleaner but the reality is that the existing statements are appended 
to the new one (only applying to new work) rather than the new license 
replacing the old one since you don't have the legal authority to 
replace it.

The libpng license is included for viewing in a great many of the 
consumer devices that I own (Blu-ray player, DVD player, TV, phone, 
etc.).  It is reproduced in many application installers and operating 
systems.  This makes it a broadly published license copied to millions 
of devices (perhaps approaching or even surpassing a billion).

Take care not to muddy things up further while trying to tidy up the 
license.

Bob
-- 
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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