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Re: LGPL vs. GPL

From: Ciaran O'Riordan
Subject: Re: LGPL vs. GPL
Date: Thu, 31 Jul 2008 11:38:27 +0100
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux)

Hi John,

These cases are never black and white, and I don't know PocketCAS or
MimeTex, so I can't give any advice on this situation, but here are some
general ramblings anyway...

If PocketCAS is written to specifically work with MimeTex, then PocketCAS
might be a "derived work" which would mean he needs your permission to
distribute PocketCAS.  Because your software is GPL'd, "needing your
permission" means he can either (a) distributing his software under the GPL
or a GPL compatible licence such as the LGPL or Revised BSD or (b) ask you
for an exception.

If PocketCAS only performs simple data exchange with MimeTex, such that
other applications could be substituted for MimeTex, then it's likely that
PocketCAS is not a derived work and so it does not need a GPL compatible

> I'm inclined to say, "Go ahead and distribute a binary image of mimetex
> along with your PocketCAS."  Is there any open-source-related reason 
> (or any other reason) I shouldn't say that?

One thing that's for sure is that he'll have to distribute MimeTex's source
with the binary (or an offer to send people the source on request).

About his request for clarification of which version of GPL MimeTex is
under.  It's a good idea to answer that request anyway.  Version 3 is the
current version, and here's an explanation of the improvements in it:

> Should I maybe instead
> say something like, "Permission is granted to distribute mimetex with
> free versions of PocketCAS, but not with commercial versions."?

That probably isn't a good idea.

You could only make such a demand *if* he does need your permission to
distribute PocketCAS (i.e. if PocketCAS is a derived work of MimeTex).  And
if that was the case, it would be better to inform him that he has to
distribute his software under the GPL.  Granting exceptions lessens the
incentive for any related project to release their software as free

As for the general request, if this developer is not helping you in any way,
and since he's not helping society in anyway, I don't see the incentive to
give him the explicit permission he's asking for.

Getting a definitive answer would take time/work and might need a lawyer.
(And you would need a copy of PocketCAS so that you could see how it
interacts with MimeTex.)  And since he's the benefactor, this work/cost
should be his.

So in general I'd recommend against granting such exceptions, but without
the details, I can't give real advice, and it's your decision anyway.  At
the very least, I'd ask that every place that says "Copyright PocketCAS",
should also say "MimeTex is copyright John Forkosh can be redistributed as
free software under the GNU GPL v3" (assuming v3 is the version you're
using).  This is to avoid the situation where users either don't know that
it's MimeTex (not PocketCAS) that is producing the high quality output, or
without knowing that they can get the source, modify, contribute, and
redistribute MimeTex.

CiarĂ¡n O'Riordan, +32 477 36 44 19,

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