GPL and closed source

Carlo Wood carlo at
Thu Jul 12 16:22:47 UTC 2001

On Thu, Jul 12, 2001 at 07:39:21AM -0700, Greg Herlein wrote:
> > Let's say that I've developped a programm under GPL.
> > Is it possible to create Closed-source plugins for the GPL programm and sell
> > them ?
> If you own the copyright to the larger framework, this can be
> done legally.  You'll want to make sure that you either
> completely own, or have disclaimers or assignment of rights
> documents from all developers.  If the framework is yours, you
> can take all or part of it closed source at will - you own it.
> However, if the framework is not clearly under your copyright,
> then you can't do this, since you cannot link closed source to an
> open source framework - and pluggable modules are considered to
> be linking.

Selling closed source plugins wouldn't be illegal anyway,
but wouldn't it be illegal for the buyers to link the bought
plugins with the GPL-ed opensource?  If so then that means that
together with selling a plugin you'd have to give a version of
the open source program under a different license, and that
means that the buyers are not allowed to link their plugins
with a later distributed, modified, GPL-ed version.

Therefore, the only way seems to be to use a GPL license with
an exception from the start (which also can only be done if you
are the copyright holder) that says that these plugins will
be excluded from the GPL.  I am not sure if such an exception
wouldn't cripple the GPL in the sense that you'd need signed
disclaimers or assignment of rights documents from all developers
despite that they send you patches for the work that already
included the exception.

I am interested in this myself, so if anyone can enlighten me:
lets take the following similar example:
section "The Qt Public License (QPL)." says:

   If you want to release your program under the GNU GPL, you can easily do that.
   You can resolve the legal conflict for your program by adding a notice like this
   to it:
       As a special exception, you have permission to link this program
       with the FOO library and distribute executables, as long as you
       follow the requirements of the GNU GPL in regard to all of the
       software in the executable aside from FOO.

Now suppose someone modifies this work and redistributes it.
Is it then such that this exact license still holds, automatically?
Including this exception thus?  I ask this because I thought that
the GPL worked solely because it GIVES right, and not takes them.
But after adding this exception you'd need signatures from other
authors, perhaps.

Carlo Wood <carlo at>

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