Re: The GPL "Special Exception" and yacc.c

[Akim Demaille]

Le 12 mars 09 à 16:25, David Wootelhoff a écrit :

> On 3/6/09, David Wootelhoff <address@hidden> wrote:
>
> > I'm considering using a Bison generated parser in a closed source
> > commercial product.
> >
> > I see that the C file output by Bison has a section starting "As a
> > special exception" which refers to "the Bison parser skeleton". Does
> > this paragraph mean I can modify yacc.c itself (which I understand is
> > the skeleton) and still keep my generated parser closed source? My
> > initial interpretation was that this was indeed the case, but I see
> > that yacc.c itself only contains the standard GPL notice and no
> > "Special Exception". (I'm aware that the special exception definitely
> > applies to the bison generated C file).
> >
> > I'd like to use Bison with a modified skeleton but I don't want to
> > violate the GPL. Any clarification is much appreciated.
>
> Hi, does anyone know the answer to the above question, or have any
> hints about how I might find it?
>
> I'm unsure if the question is so trivial that no-one is interested in
> answering it, or so difficult that people can't answer it ;)

Hi,

I am not sure about this.  As a matter of fact, of the three  
maintainers, the one who was really "in charge" of legal matters no  
longer spends time on Bison.  I'm tempted to say that, no, you can't  
do that, because I believe this is not the spirit in which we made  
Bison.  The point is to avoid people share their improvements, but  
keep their products.  So the exception really means: "if you change  
the skeleton, the changes must be GPL'd, with or without the exception  
clause, at your option."

Bison is actually late on license issues, as we did not move to the  
GPL v3.  Yet, maybe some one at the fsf help us?

The output parsers read:

/* A Bison parser, made by GNU Bison 2.4.194-c20a1-dirty.  */

/* Implementation for Bison's Yacc-like parsers in C

   Copyright (C) 1984, 1989, 1990, 2000, 2001, 2002, 2003, 2004,  
2005, 2006,
   2007, 2008 Free Software Foundation, Inc.

   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 3 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, see <http://www.gnu.org/licenses/ 
>.  */

/* As a special exception, you may create a larger work that contains
   part or all of the Bison parser skeleton and distribute that work
   under terms of your choice, so long as that work isn't itself a
   parser generator using the skeleton or a modified version thereof
   as a parser skeleton.  Alternatively, if you modify or redistribute
   the parser skeleton itself, you may (at your option) remove this
   special exception, which will cause the skeleton and the resulting
   Bison output files to be licensed under the GNU General Public
   License without this special exception.

   This special exception was added by the Free Software Foundation in
   version 2.2 of Bison.  */