[darcs-users] how to redistribute darcs+Eclipse (was: Darcs API?)

David Roundy droundy at darcs.net
Sat Jun 4 16:28:26 UTC 2005


On Fri, Jun 03, 2005 at 10:47:18AM -0300, zooko at zooko.com wrote:
> 3.  Add the following text to the license:
> 
> "As a special exception, you have permission to link this program with
> code which is licensed under the Common Public Licence or the Eclipse
> Public Licence, as long as you follow the requirements of the GNU GPL in
> regard to all of the software in the executable aside from the software
> which is licensed under the Common Public License or the Eclipse Public
> License."
> 
> This would allow the redistribution of works which combined darcs and
> CPL'ed code, but it would not allow the redistribution of works which
> combined darcs and proprietary code.

This option seems best to me (assuming we go with any change at all).  I
now see (from your explanation) that although the CPL is copyleft, it is
LGPL-style copyleft, which seems non-optimal to me (i.e. it would allow a
proprietary version of darcs).  This exception would retain the full
copyleft, while allowing the creation of mixed CPL/GPL projects (which
would themselves be limited to be two-license projects).

There is the downside (regarding your other email with the diagrams) that
we'd have to drop the exception for any GPL code that gets incorporated
into darcs (e.g. git code), or contact the author, so maintaining the
exception could be a continuing headache, possibly for no benefit.  But as
long as it's not *my* headache (or a headache forced upon all darcs
developers), I'm okay with that.  Which means that I'll continue accept new
source files that are pure GPL, and the CPL exception wouldn't necesarily
apply to all files.  It would be up to the "CPL maintainer" to contact all
authors of new GPL files and get permission to add the exception.

> The reason I care about it in specific is that I downloaded the darcs
> eclipse plugin yesterday.  It came with a note "For license reasons,
> Darcs itself is not included in this software. In order to use the
> plugin, you need an executable installed on your system. You can download
> Darcs at http://darcs.net".

I would strongly assert that including a darcs executable along with the
eclipse plugin would be "mere aggregation" under the terms of the GPL, and
perfectly legal.  If you *can* use a vanilla version of darcs with the
plugin, then I don't see how the plugin could be a derived work of darcs.
If it *were* a derived work of darcs, you wouldn't be able to distribute it
either with or without darcs itself except under the terms of the GPL.

Note: when I say "strongly assert", I'm being a bit vague, because legally
I can't speak for the position of all the authors of darcs, and one of them
might sue you for copyright violation.  But if they did, I'd be willing to
act as a witness on the GPL (not that I'd qualify as an expert witness...)
stating that I don't consider the combination of a darcs executable with a
program that calls the said executable a derived work, and that packaging
them together seems to me like "mere aggregation".

> > In summary, if you (or anyone else) wanted to contact all the darcs
> > contributors to get agreement to dual-license darcs under both GPL and
> > CPL, I'd agree.  But it's not something that greatly interests me, and
> > I'm not going to go to the trouble myself.
> 
> I am willing to do the "contacting authors" work.

I'm thinking that perhaps the best option would be to ask authors to assign
copyright to me.  I didn't want to do this, but it would definitely
simplify future changes of license.  I definitely don't want to force
contributors to assign copyright, but making it easy might be a good idea,
just to avoid this trouble in the future.  And I suspect that many darcs
contributors would be more willing to trust my judgement than to add a new
copyright exception that they might not want to bother reading up on
enough to fully understand.

Also, if we had copyrights assigned to me, I could be more specific in
creating exceptions as needed (since every exception wouldn't require
contacting 50 authors), and could add exceptions specifically for a given
purpose.  I.e. an exception that says what I said above as a personal
opinion, but in a legally binding manner.
-- 
David Roundy
http://www.darcs.net




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