Questions related to dbus

Simon McVittie simon.mcvittie at
Thu Feb 26 02:59:26 PST 2015

Responses inline below.

You might also want to consider using GDBus (part of GLib) instead of 
libdbus (part of dbus): in my opinion it is a better implementation of 
the D-Bus protocol than libdbus, and it is also licensed under the LGPL, 
a weaker (more permissive) copyleft than the GPL.

You would probably still have to distribute the dbus-daemon and other 
tools from dbus, but if you avoid linking your proprietary code to 
libdbus, the resulting executable would not have to be a derivative work 
of libdbus, so it would not inherit the GPL's copyleft requirements even 
if you chose to use libdbus under that license.

On 26/02/15 09:57, Sathish, Karthika IN BLR STS wrote:
> The following is mentioned in some files:
> a)‘ /Licensed under the Academic Free License version 2.1/’ and ‘/This
> program is free software; you can redistribute it and/or modify it under
> the terms of the GNU General Public License as published by the Free
> Software Foundation; either version 2 of the License, or(at your option)
> any later version/.’

I believe the intention here is that, because it says "Licensed under 
the AFL", you may choose the AFL; and because it says "you can 
redistribute and/or modify it under GPL-2+", you may do that. If you 
don't like one of those options, ignore it and choose the other. This is 
certainly how Collabora have interpreted dbus' license.

I cannot speak for every dbus copyright holder, and in particular, the 
parts written by CodeFactory AB have an unknown owner at this point, 
because that company went out of business, so their copyright interest 
in D-Bus is presumably now owned by their creditors. However, I am not 
aware of any dbus copyright holders who do not agree with that 
interpretation, and other large companies with expensive lawyers have 
distributed dbus under one of those licenses (rejecting the other) 
without any complaint from the dbus copyright holders.

A few years ago, the majority of dbus copyright holders (including Red 
Hat, Collabora, Nokia etc.) gave permission to relicense it under the 
MIT/X11 license as used by Expat. Unfortunately, some of the code 
contributed by CodeFactory AB is fairly central, and we were unable to 
get permission to relicense that (I can't remember whether someone found 
the copyright owner but could not get their permission, or whether we 
couldn't even find who owns it now), so we could not complete this plan.

If someone (perhaps Siemens) can track down who owns those parts and 
talk them into selling their copyright interest in dbus, it might still 
be possible to get it relicensed to something more permissive, but 
unfortunately it is not a trivial task.

> b)‘/Licensed under the Academic Free License version 2.0/’ and ‘/This
> program is free software; you can redistribute it and/or modify it under
> the terms of the GNU General Public License as published by the Free
> Software Foundation; either version 2 of the License, or (at your
> option) any later version/.’

Which file(s)? This is probably something that was missed during 
relicensing from AFL-2.0 to 2.1.

The only one I found in a quick search is dbus/ which 
appears to be © Red Hat (only), so we probably already have permission 
from the copyright holder to relicense that one to MIT/X11, which is 
strictly more permissive than AFL-2.1; or maybe someone from Red Hat 
could confirm that AFL-2.1 is OK.

> c)‘/released under the D-Bus licenses, GNU GPL version 2 (or greater)
> and AFL 1.1 (or greater)/ without wording ‘your choice’ mentioned in the
> above sentences.

Which file(s)? However, the intention here is probably "you may choose 
GPL-2, any later GPL, AFL-1.1 or any later AFL".

> If we consider both licenses, the
> GPL license will be automatically selected and it will lead to a
> copyleft effect.

Please note that some files in the tools/ directory are licensed under 
GPL-2+ (only), without an AFL option. These are D-Bus-related tools 
rather than part of the libdbus shared library that you would normally 
link into your own code, though: the practical effect is equivalent to 
distributing something like busybox.

> The list of the files having both AFL AND GPL license
> are mentioned in the document embedded in this email:-

You didn't include a document. (We would prefer plain-text on this 
mailing list anyway, though.)

> It is mentioned in ‘COPYING’ file: ‘switch to Academic Free License
> version 2.1 instead of 2.0, to resolve complaints about patent
> termination clause. Can we select Academic free license V2.1 instead of
> Academic free license V2.0.

I do not represent the copyright holder of any AFL-2.0 code, so I can't 
answer this; it looks as though that would be Red Hat.

> It is mentioned that Communications Engine (Ice)</a> is a powerful IPC
> mechanism more on the level of SOAP or CORBA than D-Bus.  Ice has a
> "dual-license" business around it; i.e. you can use it under the GPL, or
> pay for a proprietary license. Can you please explain about this ‘ pay
> for proprietary license’ option?

It is a statement about Ice, which is not D-Bus, so it is not relevant 
to the licensing model of D-Bus.

We cannot offer any alternative license for D-Bus as a whole, because 
every copyright holder would have to agree, including whoever now owns 
the parts contributed by CodeFactory AB. If we had been able to get 
agreement from every copyright holder, we would already have licensed it 
under the MIT/X11 (Expat) license, which is fine for linking to 
proprietary code anyway.

Simon McVittie
Collabora Ltd. <>

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