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

[Greg Troxel <gdt@ir.bbn.com>]

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

This is a lose; it makes guile harder to use in proprietary software,
and that doesn't serve the project's goals now.  For example, I put
guile into gated, and gated's licensing is painful enough as is
without having to figure out if it is really LGPL compatible.

  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.

This is reasonable.  I'd fall back to no bignum support, so that the
code doesn't have to be maintained.  I suspect people in embedded
environments (the target audience for whom LGPL is problematic) don't
care about bignums.  (I've never particularly cared in the places I've
embedded guile (a home-grown emulator and gated), because the
underlying programs don't really support them, so this strategy would
not have actually caused me any grief.)

  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.

I'd ask, and see what happens - I can imagine people saying no, but
not reasonably getting really upset at being asked.  The exception
could apply to GMP as used by guile, and not extend to using the GMP
api directly in derived works.  Something like the following, heavily
ripped off from the guile exception:

 * As a special exception, the Free Software Foundation gives permission
 * for additional uses of the text contained in its release of GMP.
 *
 * The exception is that, if you link the GMP library with other files
 * to produce an executable solely because GMP is required for GUILE,
 * and the resulting work does not call any GMP routines except
 * indirectly as a result of using GUILE, this does not by itself
 * cause the resulting executable to be covered by the GNU General
 * Public License.  Your use of that executable is in no way
 * restricted on account of linking the GMP and GUILE library code
 * into it.
 * 
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the Free
 * Software Foundation under the name GMP when used as a component of
 * GUILE.  If you copy code from other Free Software Foundation
 * releases into a copy of GMP, as the General Public License permits,
 * the exception does not apply to the code that you add in this way.
 * To avoid misleading anyone as to the status of such modified files,
 * you must delete this exception notice from them.
 *
 * If you write modifications of your own for GMP, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.  */

  4) Abandon GMP and continue to do things ourselves.

This is a lose, too - it seems like wasted effort to maintain multiple
copies of similar code, and it really seems the GMP code is better.

        Greg Troxel <gdt@ir.bbn.com>

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