Roman Leshchinskiy:
Manuel M T Chakravarty wrote:
* You can link a BSD3 program with a GPL'ed library and distribute
the result. (This opinion is supported by the FSF listing BSD3 as
a GPL-compatible license on their web pages and this item in their
licensing FAQ: <http://www.fsf.org/licensing/licenses/gpl-faq.html#LinkingWithGPL
>.)
Two licenses are compatible (at least in FSF speak) if you can
combine code distributed under the two licenses and distribute the
result. That is, there must be a license under which the combined
work can be distributed. In this particular case, that license is
the GPL and that's the license under which your binary package ought
to be distributed.
It would be possible to distribute GHC itself under BSD3 and
readline under the GPL if they were really distributed as two
independent thing (and, e.g., optionally linked together during
installation). But by prelinking them, you have created a combined
work which must be distributed under the GPL since it includes
GPL'ed code.
Yes, but what does that mean. It means that GHC must fullfil all the
obligations placed on us by the GPL. Well we do that by distributing
GHC under BSD3.
* That it is sufficient to include both BSD3 and GPL in the click
through license agreement of an installer, saying that GHC is under
BSD3 and readline under GPL. (What's the alternative? To dual
license GHC in that agreement? That's probably impossible as it
AFAIK would require a unanimous decision by *all* copyright holders
of portions of GHC's source code, which is quite a large number of
people.)
The reason that the FSF considers BSD3 to be compatible with the GPL
is precisely because you can take BSD3-licensed code and
redistribute it under the GPL. The copyright holders have already
given you permission to do that by using the BSD3 license - it
places no constraints on how you license the code as long as you
meet its conditions. Note that the original code is still available
under BSD3; it's just that *you* chose to distribute it under the GPL.
At least that's the view of the FSF (IIUC). The OpenBSD guys think
differently, for instance.
I don't think it matters how the OpenBSD guys think. We use code form
the FSF (ie, readline...well, ok, code from GNU) and we follow the
intention that FSF/GNU expressed by placing readline under the GPL.
As to clicking through the license agreement, take a look at
http://www.gnu.org/licenses/gpl-faq.html#ClickThrough
Basically, clicking through the license isn't necessary because it
covers distribution, not use (in contrast to a EULA).
Yes, it's not necessary for users to accept the license, but I think
it is nice to inform user about what they are installing. Moreover,
if I am not mistaken, one obligation that the GPL does place on us is
to inform users about the fact that the code is free software and that
they have the freedoms asserted under the GPL. (This might actually
be a point where other readline-enabled binary distributions of GHC
fall short.)
Manuel
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