Qt and the GPL

[kmself at ix.netcom.com]

On Mon, Sep 04, 2000 at 01:30:39PM -0700, David Johnson wrote:
> For those who not yet heard, the Qt 2.2 library will be released under
> the GPL on Wednesday. It will also be available under the QPL and a
> proprietary version as well. (see the announcement at www.trolltech.com)
> 
> I have no idea yet whether this means that Qt will be dual-licensed
> under both the QPL and GPL, or if there will be separate versions. But
> it raises some interesting questions.

My read was triple-licensing:

   Qt:   Proprietary products
   QPL:  Non-GPLd free software (eg: BSD, Artistic, etc.)
   GPL:  GPLd free software

> If there will be separate versions (and I hope there won't), then this
> will be the first time (that I am aware of) that a GPLd library will
> be available with an identical non-GPL version. 

Not quite.  Apache has dualed Artistic and GPL licenses for some time.
Sun announced dualing StarOffice, including translation libraries, under
LGPL and SISSL in July.  Mozilla is looking at MozPL and GPL for its own
code, with possible use of LGPL for libraries.

I've been a strong proponent of dual (or multi) licensing for a while, I
see it resolving a number of issues of license compatibility.  Note that
Troll is explicitly selecting GPL over LGPL for libraries to preserve
rights for proprietary use under the terms of the Qt license -- they are
preserving a proprietary business model while promoting free software at
the same time.  It's an interesting strategic ploy.  

Conversely, Mozilla and Sun are explicitly looking at leveraging free
software through the *LGPL* for library components of the respective
projects (though, AFAIK, Mozilla hasn't announced an LGPL policy though
it's being considered -- given the project's goals it may be a good
choice).

> So, if one writes a program linking to the QPL version, can it be used
> with the GPL version as well? I would think that it could, and RMS has
> said it could, but I'm wondering what the legal minded think.

If the utilizing project is GPLd, yes.  If not, no.

> And if it is to be dual-licensed, doesn't that mean that one gets to
> pick and choose their terms? For instance, I can both link to it with
> a non-GPL application, as well as not having to submit modifications
> as patches. Any Perl users out there familiar with dual licensing
> issues?

My understanding is that you'd get terms of incorporation and terms of
transmission.  I claim right to incorporat library libqtfoo under the
terms of any one of: (Qt|QPL|GPL), but I *transmit* rights of tertiary
use under *all* of (Qt QPL GPL).  It becomes somewhat like file
permission security under Linux, though you allow *both* files and users
to have multiple group associations.  Essentially, file belongs to
groups Qt, GQL, and GPL.  If user belongs to any one group, user has
access to file.  User transmits file with all three group flags, by
default.

> And finally, how will Trolltech accept modifications? Will they be
> able to apply both the QPL and GPL to the modification at the same
> time?

Good question.  My suggestion would be to require triple-licensing terms
to be applied to modifications for inclusion in the build tree.  Any
other terms would be an invitation for problems.

My feeling is that the social dynamic of such practices, particularly if
endorsed by icons such as RMS, is that they will be both generally
accepted, and the multiple licensing terms will tend to be accepted and
propogated by community users unless there are grossly unfair or
unacceptable terms in the non-free or non-GPLd licenses.  Multiple
licensing is a powerful tool, it's not a silver bullet solving all
problems, nor a carte blanche allowing any arbitrary terms in the
non-free licensing options.  However, used judiciously, it should both
promote free software, allow proprietary use, and avoid license forking
and balkanization.

> -- David Johnson _________________________ <http://www.usermode.org>

-- 
Karsten M. Self <kmself at ix.netcom.com>     http://www.netcom.com/~kmself
 Evangelist, Opensales, Inc.                    http://www.opensales.org
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