DXPC retroactively re-licensed as BSD-2-clause, nx-libs(-lite) now really DFSG-compliant

We recently had an intensive phase while reconsidering the DFSG-compliancy of the nx-libs(-lite) code base.

TL;DR; In May 2015, all versions of DXPC released before version 3.8.1 (sometime in 2002) have retroactively been re-licensed by all previous maintainers of DXPC as BSD-2-clause.

This blog arcticle is a modified version of the nxcomp/README.on-retroactive-DXPC-license file [1] and gives an overview of the discussion thread that lead to the retroactive re-licensing of DXPC.

For the full discussion, see doc/DXPC_re-licensed::debbug_784565.mbox [2] in the nx-libs source project or #784565 on the Debian bug tracker [3].

[1] https://github.com/ArcticaProject/nx-libs/blob/3.6.x/nxcomp/README.on-re...
[2] https://github.com/ArcticaProject/nx-libs/blob/3.6.x/doc/DXPC_re-license...
[3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=784565



In May 2015, a serious license issue around the nxcomp code shipped in this source project was raised and solved on the Debian bug tracker (thanks to Francesco Poli and many others): http://bugs.debian.org/784565

From: "Francesco Poli \(wintermute\)" 
To: Debian Bug Tracking System 
Date: Wed, 06 May 2015 19:35:32 +0200

I noticed that the debian/copyright states:

| Parts of this software are derived from DXPC project. These copyright
| notices apply to original DXPC code:
|    Redistribution and use in source and binary forms are permitted provided
|    that the above copyright notice and this paragraph are duplicated in all
|    such forms.
|    Copyright (c) 1995,1996 Brian Pane
|    Copyright (c) 1996,1997 Zachary Vonler and Brian Pane
|    Copyright (c) 1999 Kevin Vigor and Brian Pane
|    Copyright (c) 2000,2001 Gian Filippo Pinzari and Brian Pane

This license lacks the permission to modify the DXPC code.
Hence, the original DXPC code does not appear to comply with the
DFSG. And the nx-libs-lite is in part derived from DXPC code.

This basically means that nx-libs-lite includes parts which are
non-free (as they are derived from non-modifiable code) and
are also possibly legally undistributable (as they are non-modifiable,
but actually modified). The combination with the rest of nx-libs-lite
(which is GPL-licensed) may also be legally undistributable (since
the license with no permission to modify is GPL-incompatible).

If there's anything I misunderstood, please clarify.

Otherwise, please address this issue as soon as possible.
The copyright owners for the original DXPC code should be
contacted and persuaded to re-license under GPL-compatible

The issue has been settled by asking all recent maintainers (i.e., copyright holders) of DXPC, to agree on considering the BSD-2-clause license (as introduced in DXPC 3.8.1) retro-actively as the license of all pre-3.8.1 DXPC releases.


Kevin Vigor, the (at that time being) latest known maintainer of DXPC replied back immediately and provided the info given below. He also stated that he agrees to applying BSD-2-clause retroactively to all pre-3.8.1 releases of DXPC.

From: Kevin Vigor 
To: Mike Gabriel 
CC: 784565@bugs.debian.org, [...]
Subject: Re: Bug#784565: nx-libs-lite: parts are derived from non-free code

Hi Mike, et al,

   I am not the original author of dxpc, that being Brian Pane. However,
   I took over maintenance circa 1999 and am still the primary maintainer
   (though the project has effectively been dead for most of a decade

   As you are aware, when I inherited the code, it was licensed under a
   variant of the BSD license that did not include the 'with
   modification' clause. To the best of my recollection, somebody from
   the FSF contacted me circa 2001 regarding this and as a result,
   subsequent releases were done under a standard 2-clause BSD license
   with the modification clause. Again, to the best of my recollection, I
   contacted Brian about this change and he offered no objection.

   Further, I recall distinctly that NoMachine contacted me and
   explicitly asked permission before including DXPC code in NX, which I
   happily granted with no new conditions beyond the BSD license already
   in play.

   It is possible, though by no means certain, that I could dig up
   ancient email to corroborate this account if necessary. However, I am
   more than willing to publicly state that I believe NoMachine's use of
   DXPC code to be both legal and ethical, and that my intent when
   changing the license to 2-clause BSD was simply to clarity the
   existing intent and that it ought therefore be considered retroactive.

      Kevin Vigor



We were not able to dig out any recent mail address of Zachary Vonler, another of the DXPC copyright holders, but a phone number.

On Friday, May 15th, I (Mike Gabriel) called that phone number and left a message on - hopefully - Zach's voicebox, asking him to mail me, so I could explain everything. He mailed back and later on posted the below statement to the Debian BTS, also expressing his agreement to the retroactive re-licensing of DXPC.

Date: Mon, 18 May 2015 10:05:38 -0500
Subject: Re: Bug#784565: nx-libs-lite: parts are derived from non-free code
From: Zach Vonler 
To: 784565@bugs.debian.org

On Thu, 14 May 2015 05:55:42 +0000 Mike Gabriel <
mike.gabriel@das-netzwerkteam.de> wrote:

> TL;DR; So here comes my actual question: are you (Brian Pane, Zachary
> Vonler, Gian Filippo Pinzari) ok with retroactively regarding
> pre-3.8.1 code of DXPC (that you probably all worked on at that time)
> as BSD-2-clause? Are you ok with others having taken or taking the
> pre-3.8.1 DXPC code and distribute it in a modified form?

> A yes from all of you as DXPC copyright holders is essential for the
> continuation of nx-libs development under a free license. This may
> also possibly be an issue for NXv4 in case parts of it have been
> derived from DXPC.

Yes, I am fine with considering the license change to be retroactive to
cover the time I was the maintainer.

I have no objections to others distributing modified versions of that code.



By 18th May 2015, Brian Pane had not mailed back to us. Hoping he is well and alive. Giving my personal gratitude to him for his work on DXPC back in the nighties.

However, Kevin found an old archive of the DXPC mailing lists, esp. a post by Brian expressing openness to modifications of all DXPC code versions.

We refer to this regarding his consent on the re-licensing.

Date: Mon, 18 May 2015 15:11:42 -0600
From: Kevin Vigor 
To: Mike Gabriel ,  784565@bugs.debian.org, Francesco Poli 
CC: [...]
Subject: Re: Bug#784565: nx-libs-lite: parts are derived from non-free code

By the way, poking around the interwebs I find there is an archive of the old DXPC mailing list available at:


I think you will find this of particular interest:


List:       dxpc
Subject:    Re: future tecnologies
From:       Brian Pane 
Date:       1999-07-02 16:42:18
[Download message RAW]

Kevin Vigor  wrote:
> On 01-Jul-99 dxpc@mcfeeley.cc.utexas.edu wrote:
> > Speaking of licensing, are you putting your 3.8.0 changes to the dxpc
> > code itself under GPL, or are they going to use the original dxpc's
> > licensing?
> No, as you can probably guess, I am no fan of the GPL. For stuff on
> this level, where my hacking is pretty simple and probably devoid of
> commercial value, I'll just release my changes to the public domain and
> give up even a copyright interest in them.
> Your and Zach's copyrights still stand, of course.
> I *think* that fact that we use the LZO library and API, but do not
> directly incorporate the code, allows us to escape the clutch of the GPL
> virus.
> btw, is there an original dxpc license? I haven't seen anything but a
> copyright notice, which to my non-lawyerly mind translates as "free to
> all the world as is, negotiate with copyright owner if modifying or
> including in some other product".

The copyright banner in the Readme is all the documentation there's ever
been.  My intent was to allow _any_ distribution, use, and modification
of the source, without imposing restrictions on the licensing style of
any system into which others might incorporate the code.  We probably
should start stating this clearly in the distributions.


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Last but not least, Kevin informed us that Gian Filippo Pinzari never contributed any code to any of the official DPXC releases. So we assumed that his copyrights on the code stem from the time where he - under the NoMachine umbrella - worked on the code and should probably be associated with the GPL-2 re-licensing of the code later on done by NoMachine (which we did in the LICENSE file).

It also appears, that there has been an incongruity between the copyright statement in nxcomp/Misc.cpp and nxcomp/LICENSE for Gian Filippo Pinzari. We used the copyright years (2000,2003) from nxcomp/Misc.cpp instead of those originally given in nxcomp/LICENSE (2000,2006).

Date: Mon, 18 May 2015 19:16:25 -0600
From: Kevin Vigor 
To: Francesco Poli ,
 Mike Gabriel 
CC: 784565@bugs.debian.org, [...]
Subject: Re: [pkg-x2go-devel] Bug#784565: Bug#784565: nx-libs-lite: parts are derived from non-free code

On 5/18/2015 4:14 PM, Francesco Poli wrote:
> If it is confirmed that Gian Filippo contributed to the forking of
> DXPC within the NoMachine project, but not directly to DXPC, then I
> think that he made his contributions available under the terms of the
> GPL v2 of the NoMachine project. If this is the case, no feedback
> should be required from his side.
I can confirm that Gian Fillippo never contributed directly to DXPC.
You'll note his name does not appear in the DXPC README, and never has.