[sword-devel] The FSF's Views on GPL-covered Libraries

[Jeremy Erickson]

	Earlier I asked licensing at gnu.org about using non-GPL (but GPL-compatible) 
licenses for software that uses GPL'd libraries, to see what their 
perspective on the issue was.  Following are the messages I sent and the 
replies I received.  Please note that I am not trying to spite Crosswire and 
will license the Sword plugin solely under the GPL (though BibleMemorizer 
will of course be MIT/X11).  This is just what the FSF thinks.

----------  First Message  ----------

Subject: GPL-covered Libraries
Date: Lun 11 Abr 2005 4:25 PM
From: Jeremy Erickson {address I don't want spammed}
To: licensing at fsf.org

	I have a question about the GPL that I have seen conflicting views on.  If I
write a program that uses libraries available only under the GPL, do I have
to license my code (including portions that use the API) under the GPL, or
can I use a different GPL-compatible license instead?  Suppose I can, and
that I used the X11 license for a program.  When would each license be
applicable?  I have seen an alleged quote from Richard Stallman:

	"So if you want to write a non-copylefted application, release it under
the X11 license, and link it with a GPL-covered library, that is
allowed. The linked executable would be covered by the GPL, of
course, but the app source code would be covered by the X11 license
alone."

	Do you know if this quote is authentic?  If it is, it would seem to say that
no GPL restrictions apply to the source code, but the GPL must apply whenever
binaries are distributed.  Is this the case?  For instance, suppose I write a
program using GPL'd libraries and distribute it to someone else.  If he/she
wants to further distribute the unmodified binary, must he/she include the
source code (or an offer for the same) as required by the GPL?  Or if someone
wrote a proprietary library with the same API, could my code be linked to it?

	Also, suppose I use a library under a license that explicitly allows linking
from non-GPL Free Software (such as the QPL), and I release the code under a
GPL-compatible license such as the X11 license.  Can users who only have
access to a GPL-covered version of the library distribute binaries of my
program?  This could be the case with Qt, as version 4 for Windows will
likely be available under the GPL alone, but I can use the QPL when
developing on GNU/Linux.  When I asked Trolltech this question, they told me
I would have to ask you.

	Thanks for your time.

-Jeremy Erickson

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----------  First Reply  ----------

Subject: [gnu.org #232512] Fwd: GPL-covered Libraries
Date: Jue 21 Abr 2005 4:15 PM
From: "Dave Turner via RT" <licensing at fsf.org>
To: {the addresses I don't want to expose to spam}
Cc: licensing at gnu.org

> [{an address I don't want spammed} - Thu Apr 21 08:40:29 2005]:
> Subject: GPL-covered Libraries
> Date: Lun 11 Abr 2005 4:25 PM
> From: Jeremy Erickson {an address I don't want spammed}
> To: licensing at fsf.org
>
> 	I have a question about the GPL that I have seen conflicting
> views on.  If I write a program that uses libraries available only
> under the GPL, do I have to license my code (including portions that
> use the API) under the GPL, or can I use a different GPL-compatible
> license instead?

You can use a different license, so long as the work as a whole, and
each of its parts, can be distributed under the terms of the GPL.

To put it another way, a licensor under the GPL can't force you to
enforce GPL rights for your code -- if you want to issue a strictly more
permissive license for what you have written, nobody can stop you.

> 	"So if you want to write a non-copylefted application, release
> it under the X11 license, and link it with a GPL-covered library, that
> is allowed. The linked executable would be covered by the GPL, of
> course, but the app source code would be covered by the X11 license
> alone."
>
> 	Do you know if this quote is authentic?  If it is, it would seem
> to say that no GPL restrictions apply to the source code, but the GPL
> must apply whenever binaries are distributed.  Is this the case?

That's not how I read that quote.  The logic here is a bit complex, but
the heart of the matter is that source code for software which links to
GPL libraries does need to be licensed *compatibly* with the GPL.

>  For
> instance, suppose I write a program using GPL'd libraries and
> distribute it to someone else.  If he/she wants to further distribute
> the unmodified binary, must he/she include the source code (or an
> offer for the same) as required by the GPL?

Yes.

> Or if someone
> wrote a proprietary library with the same API, could my code be linked
> to it?

No; you may not link GPL software and proprietary software (modulo the
exception in section 3).

> 	Also, suppose I use a library under a license that explicitly
> allows linking from non-GPL Free Software (such as the QPL), and I
> release the code under a GPL-compatible license such as the X11
> license.  Can users who only have access to a GPL-covered version of
> the library distribute binaries of my program?  This could be the case
> with Qt, as version 4 for Windows will likely be available under the
> GPL alone, but I can use the QPL when developing on GNU/Linux.  When I
> asked Trolltech this question, they told me I would have to ask you.

I must admit I'm confused about what you're asking here.  But I don't
really have time to answer hypothetical questions -- if there is some
actual situation here, could you present that?


[footnote 1] http://rebecca.hitherby.com/archives/000452.php

--
-Dave "Novalis" Turner
GPL Compliance Engineer
Free Software Foundation

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----------  Second Message  ----------

Subject: Re: [gnu.org #232512] Fwd: GPL-covered Libraries
Date: Jue 21 Abr 2005 5:33 PM
From: Jeremy Erickson {address I don't want spammed}
To: licensing at fsf.org

> > Or if someone
> > wrote a proprietary library with the same API, could my code be linked
> > to it?
>
> No; you may not link GPL software and proprietary software (modulo the
> exception in section 3).

I'm not sure you got what I was saying here.  Let's say, for example, that I
wrote a program that linked with Readline.  Suppose I licensed it under the
X11 license.  Then, suppose Microsoft wrote a new proprietary library that
was API compatible with Readline.  Could my code be recompiled against
Microsoft's Readline clone?  No code that was exclusively under the GPL would
actually be used at all during this compilation, only during the initial
development.  It would seem that if Wine is legal, this would be as well.

> > 	Also, suppose I use a library under a license that explicitly
> > allows linking from non-GPL Free Software (such as the QPL), and I
> > release the code under a GPL-compatible license such as the X11
> > license.  Can users who only have access to a GPL-covered version of
> > the library distribute binaries of my program?  This could be the case
> > with Qt, as version 4 for Windows will likely be available under the
> > GPL alone, but I can use the QPL when developing on GNU/Linux.  When I
> > asked Trolltech this question, they told me I would have to ask you.
>
> I must admit I'm confused about what you're asking here.  But I don't
> really have time to answer hypothetical questions -- if there is some
> actual situation here, could you present that?

I'm writing a program called BibleMemorizer which uses Qt.  I would like to
license it under the license OSI calls the "MIT License" and you list as the
"Expat License" on your license list page.  On GNU/Linux this is explicitly
permitted under the QPL.  When Qt 4 is released on Windows, however, it will
probably be exclusively under the GPL.  From what you said earlier in your
message, it appears that it could be used on Windows after Qt 4 is released
without legal difficulty, since the Expat license is listed in the
GPL-compatible section.  Is this indeed the case, or would I have to
explicitly dual-license the code under the GPL and the MIT/Expat License?

Thanks.

-Jeremy Erickson

-------------------------------------------------------

----------  Second Reply  ----------

Subject: [gnu.org #232512] Fwd: GPL-covered Libraries
Date: Lun 25 Abr 2005 5:13 PM
From: "Dave Turner via RT" <licensing at fsf.org>
To: {addresses I don't want spammed}
Cc: licensing at gnu.org

> [{an address I don't want spammed} - Thu Apr 21 18:36:41 2005]:
> > > Or if someone wrote a proprietary library with the same API, could
> > > my code be linked to it?
> >
> > No; you may not link GPL software and proprietary software (modulo
> > the exception in section 3).
>
> I'm not sure you got what I was saying here.  Let's say, for example,
> that I wrote a program that linked with Readline.  Suppose I licensed
> it under the X11 license.  Then, suppose Microsoft wrote a new
> proprietary library that was API compatible with Readline.  Could my
> code be recompiled against Microsoft's Readline clone?  No code that
> was exclusively under the GPL would actually be used at all during
> this compilation, only during the initial development.  It would seem
> that if Wine is legal, this would be as well.

Oh, I see.  That's OK, because of the "independent and separate" clause.

> > > 	Also, suppose I use a library under a license that explicitly
> > > allows linking from non-GPL Free Software (such as the QPL), and I
> > > release the code under a GPL-compatible license such as the X11
> > > license.  Can users who only have access to a GPL-covered version
> > > of the library distribute binaries of my program?  This could be
> > > the case with Qt, as version 4 for Windows will likely be
> > > available under the GPL alone, but I can use the QPL when
> > > developing on GNU/Linux. When I
> > > asked Trolltech this question, they told me I would have to ask
> > > you.
> >
> > I must admit I'm confused about what you're asking here.  But I
> > don't really have time to answer hypothetical questions -- if there
> > is some actual situation here, could you present that?
>
> I'm writing a program called BibleMemorizer which uses Qt.  I would
> like to license it under the license OSI calls the "MIT License" and
> you list as the "Expat License" on your license list page.  On
> GNU/Linux this is explicitly permitted under the QPL.  When Qt 4 is
> released on Windows, however, it will probably be exclusively under
> the GPL.  From what you said earlier in your message, it appears that
> it could be used on Windows after Qt 4 is released without legal
> difficulty, since the Expat license is listed in the GPL-compatible
> section.  Is this indeed the case, or would I have to explicitly
> dual-license the code under the GPL and the MIT/Expat License?

Yes, you can do that -- you don't need to explicitly dual-license.

--
-Dave "Novalis" Turner
GPL Compliance Engineer
Free Software Foundation

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