[ale] OT: GPL Question

[Michael Hirsch]

On Fri, 2002-08-30 at 17:48, Andrew Grimmke wrote:
> It is my understanding that this is the specific reason that the LGPL
> was developed.  So that one could use a free library and not be bound by
> the GPL. (lesser also stands for library)

Yes, that was the motivation.  But that was also before dynamic linking
was common.  I think most people agree that statically linking to GPLed
code requires the GPL for all code.  But the issue for dynamic linking
is much more vague.

Matt Asay, in his article, claims that most people agree that
dynamically linking to GPLed code does not require GPLing your code.  He
says, this, but I couldn't find any justification for this claim other
than the fact that Linus and the other kernel developers have agreed
that code can make system calls to the GPLed kernel without requiring
that the code be GPLed.  This is a far cry from linking GPLed libraries.

I also don't know of any programs that do what Asay is claiming--linking
against GPLed libraries.  Lots of proprietary code links against glibc
and other LGPLed libraries, but try releasing sealed code that links to
readline (a GPLed library) and see how long before the FSF lawyers call
you.

I do know of several software companies that dual license their
libraries as either proprietary or GPL.  The most prominent example is
Troll Tech with their qt library.  They do not agree that you can use
their GPL library to develop closed code:

 Why is Qt Free Edition not distributed under the GNU Library (or Lesser) General Public License (LGPL)?
 The LGPL is designed to "permit developers of non-free programs to use
free libraries" (quote from the LGPL). In other words, if Qt Free
Edition were LGPL'd, companies would not have to purchase the
Professional or Enterprise Edition in order to make
commercial/proprietary software, they could just use the Free Edition,
free of charge. That would mean Trolltech would not get the revenue
necessary for improving and extending Qt.
<http://www.trolltech.com/developer/faqs/free.html#Q2>

I think that you are acting dangerously if you link to GPLed libraries
with closed code.  There is a definite case to be made for it, but,
unlike Asay, I think there are very few precedents backing up such an
action.

You are, however, safe if you link to LGPLed libriries and you may make
system calls to the GPLed Linux kernel without risk.

--Michael

> Andrew
> 
> On Fri, 2002-08-30 at 16:42, Fulton Green wrote:
> > The way I understand it ...
> > 
> > The GPL is "viral". Any software you write that *links*, or binds, with a
> > GPL'd library must also become GPL'd.
> > 
> > OTOH, if the library in question is LGPL'd ("L" = "lesser"), you're not
> > obligated to license your code under GPL or LGPL as long as you don't have
> > any other similarly viral libs.
> > 
> > If you were to make a modification to the LGPL'd lib, you would need to
> > release your mods to that lib in at least a patchable form (if not the whole
> > source tree) along w/your software binaries.
> > 
> > The GNU C library and the majority of other popular libs are LGPL'd.
> > 
> > Libraries that are "BSD'd" (i.e., Berkeley-style license) are much less
> > viral.
> > 
> > All this is extreme generalization, so read the licenses carefully and
> > consult w/your lawyer before proceeding any further. And it goes w/o saying
> > that IANAL.
> > 
> > On Fri, Aug 30, 2002 at 04:31:39PM -0400, Jeffrey B. Layton wrote:
> > >    If I install a piece of software that is licensed under
> > > GPL, say a mathematical library, and write my own
> > > code that just calls functions within the library (I
> > > have not modified the library in any way and do not
> > > statically link the library), do I have to license my
> > > code under GPL? My initial gut feel is I can license
> > > my software any way I want, but this is brewing
> > > into a controversary at work and I want to get some
> > > input (and any links) before discussing this with the
> > > attorneys.
> > 
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> 
> 
> 
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