Qt and the GPL

[David Johnson]

On Tue, 05 Sep 2000, Rick Moen wrote:
> begin David Johnson quotation:
>  
> > Okay, followup question. If a BSD application automatically converts
> > to the GPL by linking to a GPL library, can the application still be
> > distributed under the BSD license?
> 
> A licence adheres to a particular _copy_ of a copyrighted work. 

Okay, slow down. I need to digest this.

Okay, I'll buy it. I can issue one copy under the BSD, another under
the GPL, and yet a third under a proprietary license. But whether
another party can is a different matter...

> ... Take a
> third party's BSD-licenced application and link it against a GPLed
> library, and the resulting composite work can be distributed only under
> the GNU GPL, as a result of the library's licence (absent separate
> permission from the copyright holder).

The work _as_a_whole_ must be under the GPL, but the individual
components don't have to be so long as they fulfill the GPL's
distribution requirements.

> Presumably, you would have _read_ that licence before using it:
> http://opensource.org/licenses/bsd-license.html   The operative clause
> says "Redistribution and use in source and binary forms, with or without
> modification, are permitted...."  Note the _extremely_ broad set of
> permissions it grants.

Okay, two things. Copyright law does not normally allow the recipient to
change the terms of copyright or licensing. The author must give 
permission to do that. Since the BSD license does not explicitly grant
that right it does not belong to the user. A broad set of permissions
to "redistribute and use" does not include license modification.

Second, just after the clause you quote there follows "...provided that
the following conditions are met". Those conditions say that you must
"retain the above copyright notice, this list of conditions and the
following disclaimer." Even if the license allowed you to add stuff to
it, you cannot take these conditions away. It's a requirement that you
keep them.

So even if a user receives a package that contains BSD
licensed files, but is licensed as a whole under the GPL, he still has
the explicit permission to take those BSD files and redistribute them
under the terms of the BSD license. At the most, these files would be
considered akin to dual-licensed.

-- 
David Johnson
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