Thorkil Naur:
On Tuesday 12 February 2008 06:56, Manuel M T Chakravarty wrote:
Mac installer packages usually present a license to the user to
accept
during the installation process. Consequently, I added what I think
is a correct licensing document to the tree at
http://darcs.haskell.org/ghc/distrib/MacOS/installer-docs/
license.html
I have reviewed this briefly. It is not the GPL.
It is three licences. The BSD3-style GHC license, the LGPL, and the
GPL.
Elsewhere
(http://www.haskell.org/pipermail/glasgow-haskell-users/2008-February/014298.html
)
you have written:
The GHC binary in the package links statically against GNU
readline ...
The GNU readline package is under the GPL. I dont understand how you
can link
statically against the GNU readline library and not put the combined
package
under the GPL.
First of all, whether we link statically or dynamically against
readline makes no difference whatsoever. (It's only the LGPL that has
a special provision for dynamic linking.)
The way I view this is that licences form a partial order, which we
may call "restrictiveness". If license A (eg, GPL) is more
restrictive than license B (eg, BSD3), then a combined product must
satisfy the conditions of the more restrictive licence. Of course,
there are license which are incomparable under this PO and these
license are incompatible; ie, you can not combine code under these two
licenses. (Here is the FSFs definition of what it means for two
licences to be compatible: <http://www.fsf.org/licensing/licenses/gpl-faq.html#WhatIsCompatible
>.)
The important point here is that by offering code under a particular
licence you implicitly also offer it under all strictly more
restrictive licenses; i.e., if I give you code under BSD3, you can re-
distribute it under the GPL. (If you don't modify it, there is little
point, because people can get that same code from me under BSD3, but
legally you can just change the license and not the code.) This
ability to morph BSD3 into GPL is what justifies the license
information in the installer package. By offering GHC under BSD3, we
do allow people to distribute it under the GPL and hence fullfil our
obligations under the GPL (which we incurred by linking - in whatever
way - against readline). Does that clarify the point?
Manuel
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