TridiaVNC Pro and GPL: Re: Tridia VNC

Michael Ossmann michael.ossmann "at"
Fri, 08 Mar 2002 18:45:03 +0000


Thanks for posting.  It's nice that you guys are willing to discuss this
stuff publicly.  :-)

On Fri, Mar 08, 2002 at 09:03:36AM -0500, W. Brian Blevins wrote:
> I am most definitely not a lawyer.

Understood.  Neither am I.

> > Personally, I suspect there is a GPL violation going on here.  In fact,
> We respectfully disagree.  In fact, others posting to this forum
> in the past would appear to disagree as well:

It doesn't look to me like either of those posters had actually
downloaded the software and taken a close look at it before posting.
They were giving the benefit of the doubt.  (I did too until I installed
it for myself.)

> > I'm fairly certain of it.  TridiaVNC (or at least components of it)
> > are distributed as a part of TridiaVNC Pro.  It even installs a
> > TridiaVNC subdirectory which includes a copy of the GPL.  However,
> > the GPL reads:
> > 
> >   0. This License applies to any program or other work which
> >   contains a notice placed by the copyright holder saying it may be
> >   distributed under the terms of this General Public License.  The
> >   "Program", below, refers to any such program or work, and a "work
> >   based on the Program" means either the Program or any derivative
> >   work under copyright law: that is to say, a work containing the
> >   Program or a portion of it, either verbatim or with modifications
> >   and/or translated into another language.
> What precisely does the GPL define as a "derivative work"?

The GPL doesn't precisely define "derivative work", which can make these
kinds of discussions interesting.  It leaves the definition open to the
same laws which govern traditional copyright.  The definition is subject
to the interpretation of the courts.  A good rule of thumb is to put
yourself into the shoes of the original author (ORL/AT&T) and pretend
that you had released the code under a license which allows
redistribution but not modifications or derived works.  (Let's also
pretend for simplicity that TridiaVNC was the original product.) Someone
else comes along with a commercial product exactly like TVP.  If you
installed it and noticed the way it incorporates TridiaVNC behind the
scenes, would you think it was a valid redistribution, or would you
consider it an illegal derived work?

> Basically, the closed source components in TridiaVNC Pro do not link
> with the open source components.

That may be the case, but a user downloading TVP wouldn't be able to
tell the difference.  There is no indication during the installation
process that two separate products with two separate licenses are being
installed.  TVP cannot be downloaded without the GPL components.  Nor
does it appear that it would be at all useful if the GPL components were
removed.  If the user already has TridiaVNC installed, TVP doesn't
integrate with that installation at all; the TridiaVNC components of TVP
are completely separate.

If the binaries were linked, then it would definitely be a clearer case.
Even without linking, however, TVP can be said to incorporate TridiaVNC.
The two products are combined so that they are effectively a single
system.  They can't be treated as two separate programs.  I think any
court would consider TVP a derivative work for that reason.

> > TridiaVNC Pro looks like a derivative work to me.  Even if they
> > could somehow prove in court that it is not a derivative work, there
> > is a problem with the click-through license in the TridiaVNC Pro
> > installer.  It removes many of the freedoms granted by the GPL for
> > the entire piece of software without any exclusions for the open
> > source components.

This is still my biggest concern.  At the very least, the TVP installer
should make the customer aware of the existence of GPLed software within
the package and should not force the user to click through a license
which explicitly violates the GPL for those components.

I've also noticed something else that concerns me with TridiaVNC (not
TVP).  It doesn't contain the copyright notices of the various authors,
notably AT&T, Widget Workshop, Inc., and Jef Poskanzer, in the binary
distribution (I haven't looked at the source distribution).  I suspect
that some additional credits (Constantin Kaplinsky, Tim Waugh, etc.)
would also be appropriate.

Thanks again,

Mike Ossmann, Tarantella/UNIX Engineer/Instructor
Alternative Technology, Inc.
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