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

[Marius Vollmer <mvo@zagadka.ping.de>]

Rob Browning <rlb@defaultvalue.org> writes:

> If the analysis is correct,

I think it is, on every point.  I should have caught the license
problem earlier, sorry.[1]

> then it seems like we have a few choices:
> 
>   1) Use (and require) GMP anyway and expect people to accomodate the
>      licensing changes.

Personally, I would be happy to see Guile use the LGPL or even the
unmodified GPL.  It makes things easier (as shown by this very issue),
but relicensing towards more restrictions should not be done lightly.
People have said that they do make use of the exception, and taking
that choice away from them would be bad.

>   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.

I think this is acceptable.  A not-GMP-using libguile would be
technically inferior to the default libguile, but that can only be
expected.  If you want the good stuff, agree to our terms.

If it is not too much hassle, we should keep our current bignum
implementation as the fall-back.  We might have a thin interface layer
between libguile and GMP (as some SCM_I_BIGNUM_ macros say).  That
interface could be tuned to be efficiently implemented by GMP, and
straightforwardly but not necessarily efficiently implemented with the
current stuff.  What I'm trying to say is that we should not make
ourselves a lot of work to keep the fall back be efficient.

>   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.

That would be a solution, but somehow, I don't like it very much.  It
can't hurt to ask.  I am a bit unsure about my own position here, so I
would have to think about this a bit more.  I would ask RMS what he
thinks about removing the exception from libguile and about adding the
restriction to GMP. But I don't know yet in what direction I would
argue myself...

>   4) Abandon GMP and continue to do things ourselves.

That would not be good.  GMP is the technically Right Thing to use,
and it would be strange to refuse our 'own' software for its
restrictive license terms, wouldn't it?



[1] Somehow, it escaped me that the exception was not equivalent to
LGPL.  I had this image in my head where the FSF were trying a new
strategy since they didn't really seem to like the LGPL any more.  But
I also _knew_ that the exception did not turn the GPL into the LGPL.
If someone had asked me directly... :-/

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