licensing Autoconf macros

[Alexandre Duret-Lutz]

[Two parts in this mail.  First some background about the
licensing of third-party Autoconf macros in autotools.  Then
some concerns about the licensing of the macros from the
archives.]

We have recently realized that the third-party macros
distributed with Automake were labeled as GPL.  When aclocal is
run, the license of these files is copied verbatim into
aclocal.m4, but aclocal also prepends an all-permissive license
to aclocal.m4.  I.e., the contents are confusingly distributed
under two conflicting licenses.

Autoconf macro distributed by Libtool and Gettext were using a
slightly different license: GPL + the exception that "if you
distribute this file as part of a program that contains a
configuration script generated by Autoconf, you may include it
under the same distribution terms that you use for the rest of
that program."

The idea, of course is that macros distributed by these
packages need also to be distributed in packages with
incompatible licenses.

The issue was brought to RMS and the conclusion was that
 - there is no point in using an exception such as the above, 
   because
     a) an Autoconf macro can be assumed to be always used
        in a package that contains a configuration script
     b) someone could use the macro in a simple package with
        an all-permissive license to change that license...
 - it is simpler to use an all-permissive license for all these
   macros

This last item has been made official at the end of
http://www.gnu.org/prep/maintain/html_node/License-Notices.html#License-Notices

CVS Automake and CVS Libtool already use this kind of license
for macros:

# Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
# Free Software Foundation, Inc.
#
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.

I'm not sure this is as important for the archive, but I, for
one, would like to distribute my macros under such an
all-permissive license.

Here are some thoughts about the license currently used by the
macros of the archives.  I.e., GPL, plus the following
exception:

| As a special exception, the respective Autoconf Macro's
| copyright owner gives unlimited permission to copy, distribute
| and modify the configure scripts that are the output of Autoconf
| when processing the Macro. You need not follow the terms of the
| GNU General Public License when using or distributing such
| scripts, even though portions of the text of the Macro appear in
| them. The GNU General Public License (GPL) does govern all other
| use of the material that constitutes the Autoconf Macro.
| 
| This special exception to the GPL applies to versions of the
| Autoconf Macro released by the GNU Autoconf Macro Archive. When
| you make and distribute a modified version of the Autoconf
| Macro, you may extend this special exception to the GPL to apply
| to your modified version

First, this exception mentions only the bits of the macro that
appear in the configure script.  So the copy of the macro
distributed in aclocal.m4 (or alongside as we now prefer) is
still covered by the GPL.  The reason this exception work for
Autoconf is that the Autoconf macros do not have to be
distributed.  Third-party macros have to be distributed along
with the configure that use them, so I think the above text is
useless: packages using these macros do have to distribute GPL
files anyway.

However they do not know this, because the files do not say so!
This is, IMHO, a shame: every file should have an explicit
license, especially files that are meant to be shared like those.

My suggestions would be to
1) add the standard GPL blurb + the above exception + copyright owner 
   to all macros
2) ask each author whether s/he agrees to relicense his/her macros
   under an all-permissive license (I do), or plain GPL, in order
   to get rid of the above exception
3) reject new submissions without license

Note: some macros (e.g., Braden's) used to have @copyright and
@license tags, but I can't find example of these anymore.
-- 
Alexandre Duret-Lutz