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The Guile license and the use of LGPL libs (like GMP).


From: Rob Browning
Subject: The Guile license and the use of LGPL libs (like GMP).
Date: Thu, 16 May 2002 10:35:44 -0500
User-agent: Gnus/5.090006 (Oort Gnus v0.06) Emacs/21.2 (i386-debian-linux-gnu)

Marius Vollmer <address@hidden> writes:

>> I haven't checked yet, but can we use GMP's IO routines?
>
> I don't know, I haven't looked...

After posting this question, I ended up in a good discussion with Greg
Troxel about using GMP and the resultant licensing issues.  Now it may
be that the two of us are misunderstanding things, but it looks like
if we migrate to require GMP then we may be changing the licensing
requirements for apps that use Guile.  In particular, any app that
wants to link against Guile will have to respect the provisions of the
LGPL which is at least a bit more restrictive than Guile's license.  I
think Greg put the possible issues fairly clearly:

> I'm not sure how I feel personally.  It has been guile project
> policy that guile has the guile exception in order to encourage use
> of guile absolutely everywhere.  Meeting LGPL terms isn't
> necessarily hard, but it requires thought and possibly legal
> department review, whereas the guile exception is easier to read and
> get on with life.

and then in response to a question I had about whether or not dynamic
linking avoided the problem (at least for apps that didn't need to
-static link):

> Dynamic linking is not entirely sufficient to comply with LGPL;
> rights to modify for own use and reverse engineer to debug that use
> must also be granted (see section 6 of LGPL).  It may be that given
> where guile is, and perl/python/tcl, that this is really not
> important strategically to guile and the FSF as a whole.  But I
> maintain that departing from the guile exception is a substantial
> philosophical shift.  Only free software weenies seem to use guile
> as it is, so a change probably wouldn't hurt much.  And I only write
> code mostly on platforms with shlibs, but what about palmos?  What
> if cisco wanted to put guile into IOS?  LGPL compliance would not
> perhaps be intellectually problematic, but it would be a lot of
> work, so they wouldn't want to do this.

If the analysis is correct, then it seems like we have a few choices:

  1) Use (and require) GMP anyway and expect people to accomodate the
     licensing changes.

  2) Use GMP, but have a configure switch that allows you to omit it,
     either with fallback non-GMP bignum support, or perhaps no
     bignums at all.

  3) Ask the relevant parties whether or not they might be willing to
     extend the guile exception to GMP, i.e. add a special Guile
     clause to the GMP license.

  4) Abandon GMP and continue to do things ourselves.

Thoughts?

-- 
Rob Browning
rlb @defaultvalue.org, @linuxdevel.com, and @debian.org
Previously @cs.utexas.edu
GPG=1C58 8B2C FB5E 3F64 EA5C  64AE 78FE E5FE F0CB A0AD



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