Clarification about the octave-gpcl licensing conditions

[Rafael Laboissiere <rafael@debian.org>]

I am confused about the the licensing conditions of the octave-gpcl package
and I need some advise from the debian-legalers.

I am both the upstream author and the maintainer of octave-gpcl.  This
package provides the Octave (www.octave.org) binding for the General Polygon
Clipper library (http://www.cs.man.ac.uk/~toby/alan/software/). The GPC
library is released under a non-free license and is also packaged for Debian
by me (libgpcl0 and libgpcl-dev).

The problem arises because the octave-gpcl packages produces a loadable
module (or plugin) in the form of a *.oct file that is loaded by Octave at
run-time.  However, Octave is released under the GPL (not the LGPL) meaning
that it is not allowed to link any non-GPL compatible product against it and
redistribute the whole thing.  The situation seems to be similar to that of
the readline library.

My questions are: (1) should I move the octave-gpcl package from contrib to
non-free?  (2) If I could keep octave-gpcl under a GPL-compatible license
(although it links against a non-free library), wouldn't that be an
infringement of the GPL, which is Octave's license?  (3) In any event, would
it be legal at all to distribute Octave add-ons that link against non-free
external libraries?  (4) How would the situation be if Octave were released
under the LGPL?

[Please, keep Cc: to maintainers@octave.org.  I hope the cross-posting is
not abusive.  M-F-T set accordingly.]

Thanks,

-- 
Rafael