Re: [Texmacs-dev] Qt

[Joris van der Hoeven]

> Concerning the change of licence of QT from Trolltech :
> 
> Q: Can the developer of a program who distributed it under the GPL later 
> license it to another party for exclusive use?
> A: No, because the public already has the right to use the program under 
> the GPL, and this right cannot be withdrawn.

This is not exactly true: if you have the copyright on a program,
then you may change it to whatever license(s) you like.
What is true, is that a GPL-licenced program usually has been copied
all around the world. You can not forbid people to continue using
those copies and developing them further under the GPL.

> I also had a look at the Qcad licence, and I saw the following post 
> scriptum after the GPL terms :
> 
> Additionally, you are granted permission to assume, for the purposes of
> distributing this program in object code or executable form under 
> Section 3 of
> the GNU Public License, that the QT library is normally distributed with 
> the
> major components of the operating system on which the executable or object
> code runs.
> 
> As an exception to the GNU GPL, this program may be compiled and linked 
> with
> the TrollTech QT library without implying that any of the rights or
> restrictions associated with the GPL are applied to the QT library.

Right; this is the kind of thing we need. My last proposal further extends
this kind of license when you replace Qt by any other toolkit.
It also further restricts the licence in the sense that Trolltech will
*not* be permitted to distribute these binaries (without making Qt free
on the corresponding platform) and that other distributors of binaries
should make a free (beer) offer for at least three copies of the toolkit.

> A drawback of this is that we have to ask copyright owner's permission 
> if we want to incorporate code of GPL programs into the TeXmacs code.

That is indeed the problem. Additionally, if the program depends
on other GPLed software (like Guile in our case), then a similar
kind of exception is needed for each dependency...