Bug#617931: gmsh: multiple licensing issues

[Francesco Poli (wintermute)]

Package: gmsh
Version: 2.5.0.dfsg-2
Severity: serious
Justification: Policy 2.2.1

Hello again Debian Science Maintainers,
thanks for maintaining gmsh, as well.

This package is released under the terms of the GNU GPL v2 and links
with libgsl0ldbl, which is released under the terms of the GNU
GPL v3 [1].

[1] http://packages.debian.org/changelogs/pool/main/g/gsl/gsl_1.14+dfsg-1/libgsl0ldbl.copyright

This may cause a first licensing issue.
If gmsh is under the GNU GPL v2 only, I would say that the binary
package is currently undistributable, as it links with a
GPLv2-incompatible library (GPLv3 is incompatible with GPLv2).
If, on the other hand, gmsh is under the GNU GPL v2 or later, there's
no problem between gmsh and libgsl0ldbl.

The official gmsh homepage says:

| Gmsh is copyright (C) 1997-2009 by C. Geuzaine and J.-F. Remacle
| and is distributed under the terms of the GNU General Public License
| (GPL) [2] (with an exception [3] to allow for easier linking with
| external libraries). 

[2] http://www.gnu.org/copyleft/gpl.html
[3] http://www.geuz.org/gmsh/doc/LICENSE.txt

Link [2] currently describes the GNU GPL v3 and link [3] says
"GNU General Public License (GPL)" without specifying the version,
but then includes the full text of GPLv2.

It's not clear to me what the Gmsh copyright holders mean:
"GPL v2 only", "GPL v2 or later", or "GPL any version"?
I think a clarification should be asked to them.
If the answer is "GPL v2 only", then I think that the
possible solutions are:

 (1A) GSL copyright holders should be contacted and persuaded to
re-license GSL under GPLv2-compatible terms (such as "GPL v2 or
later", for instance: take into account that GSL was previously
released under GPLv2 and later switched to GPLv3...).

 (1B) GSL should be substituted with a GPLv2-compatible replacement,
if any is available.

 (1C) Gmsh copyright holders should be persuaded to re-license
Gmsh under the terms of the "GNU GPL v2 or later"


BTW, the exception [3] grants permission to combine Gmsh
with TetGen, Netgen, Chaco and METIS, but the debian/copyright file
of the gmsh package does not mention this fact.
I think that the debian/copyright file should be fixed.
Do you want me to file a separate bug report for this issue?


Another licensing issue arises since gmsh links with
libopencascade-*-6.3.0, which is released under the terms of the
(GPL-incompatible) OCTPL v6.3: this is similar to bug #617613 [4].

[4] http://bugs.debian.org/617613

I would say that gmsh (the binary package) is currently
undistributable, as it is GPL-licensed and links with both a
GPLv3-licensed library and a GPL-incompatible one.

Here are the possible solutions I can think of:

 (2A) Open CASCADE S.A.S. should be contacted and persuaded to
re-license Open CASCADE Technology under GPLv2-and-v3-compatible terms.

 (2B) Open CASCADE Technology should be substituted with a
GPLv2-and-v3-compatible replacement, if any is available.

 (2C) Gmsh and GSL copyright holders should be asked to add a
license exception that gives permission to link Gmsh and GSL with
code released under the OCTPL.

The most desirable solution is (2A): as explained in bug #617613 [4],
I need help in persuading Open CASCADE S.A.S. to switch to the GNU
LGPL v2.1, so, once again, please join me in this persuasion effort!

Thanks for any help you can provide.