Re: [Texmacs-dev] Qt

[Frédéric Parrenin]

I had a look at the terms of the GPL, and I saw the following text in 
the FAQ :



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the GPL, and this right cannot be withdrawn.



Concerning the GPLed version of TeXmacs for Win32 using QT :

Q: I am writing free software that uses non-free libraries. What legal 
issues come up if I use the GPL?

A: If the libraries that you link with falls within the following 
exception in the GPL:

    However, as a special exception, the source code distributed need not
    include anything that is normally distributed (in either source or
    binary form) with the major components (compiler, kernel, and so on) of
    the operating system on which the executable runs, unless that
    component itself accompanies the executable.

then you don't have to do anything special to use them. In other words, 
if the libraries you need come with major parts of a proprietary 
operating system, the GPL says people can link your program with them.

If you want your program to link against a library not covered by that 
exception, you need to add your own exception, wholly outside of the 
GPL. This copyright notice and license notice give permission to link 
with the program FOO:

  Copyright (C) yyyy  <name of copyright holder>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

   In addition, as a special exception, <name of copyright
   holder> gives permission to link the code of this program with
   the FOO library (or with modified versions of FOO that use the
   same license as FOO), and distribute linked combinations including
   the two.  You must obey the GNU General Public License in all
   respects for all of the code used other than FOO.  If you modify
   this file, you may extend this exception to your version of the
   file, but you are not obligated to do so.  If you do not wish to
   do so, delete this exception statement from your version.

Only the copyright holders for the program can legally authorize this 
exception. If you wrote the whole program yourself, then assuming your 
employer or school does not claim the copyright, you are the copyright 
holder--so you can authorize the exception. But if you want to use parts 
of other GPL-covered programs by other authors in your code, you cannot 
authorize the exception for them. You have to get the approval of the 
copyright holders of those programs.

When other people modify the program, they do not have to make the same 
exception for their code--it is their choice whether to do so.

Adding this exception eliminates the legal issue, but does nothing about 
the more serious problem of using a non-free library: your program won't 
be fully usable in a free environment. If your program depends on a 
non-free library to do a certain job, it cannot do that job in the Free 
World. If it depends on a non-free library to run at all, it cannot be 
part of a free operating system such as GNU; it is entirely off limits 
to the Free World.

So please consider: can you find a way to get the job done without using 
this library? Can you write a free replacement for that library?

If the program is already written using the non-free library, perhaps it 
is too late to change the decision. You may as well release the program 
as it stands, rather than not release it. But please mention in the 
README that the need for the non-free library is a drawback, and suggest 
the task of changing the program so that it does the same job without 
the non-free library.

Also please tell us (<address@hidden> <mailto:address@hidden>) about the 
non-free library and what job it does. We could encourage people to 
develop a free library to do the same job.




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.



A similar remark can be found in the FAQ from Trolltech :
http://www.trolltech.com/developer/download/qt-win-noncomm.html


To summary, yes, it is possible to licence TeXmacs under the GPL even if 
is use QT, if we add an exception outside the GPL.
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.


I hope that helps.
Regards.


               Frédéric



Marciano Siniscalchi wrote:

> Folks,
>
> not to reopen a discussion on the various merits of different GUIs, 
> but I (for my own curiosity) asked Trolltech about the licensing 
> status of Qt/X11 under Cygwin. Their Website seemed to suggest that 
> Qt/X11 was available under the GPL regardless of environment where it 
> runs, but in these matters, it's always better to get things straight 
> from the horse's mouth. Well, here's what the "horse" had to say:
>
> \begin{email_from_Trolltech}
>
> Hi Marciano,
>
> thank you for your interest in Qt. Qt/X11 is available under both an Open
> Source, free license and under the commercial license. It's Qt/X11, not
> Qt/Unix or Qt/Linux, so if you get Qt/X11 to run on a cygwin environment
> with an X11 server there is no licensing issue.
>
> [snap!]
>
> Best regards,
> Volker