[pmwiki-devel] pmwiki licensing: AGPL option?

[John Rankin]

On 1/03/11 12:47 PM, Patrick R. Michaud wrote:
> On Tue, Mar 01, 2011 at 09:50:17AM +1300, John Rankin wrote:
>> Is it possible to have an option to download pmwiki under the Affero
>> GPL [1], as well as the GPL?
>> [...]
>> Our preference is to use the
>> AGPL, so that others who may build on our work are required to
>> distribute any changes they make, if their site is public.
> This is a very interesting question.  To me, offering PmWiki under
> both the GPLv2 and AGPL seems like it could lead to a whole lot
> of confusion.  In particular, I'm not sure how we would enforce
> any of the AGPL provisions as long as a GPLv2 version exists.
> A "violator" could simply claim that their site is being built
> from the non-AGPL version of PmWiki, and thus they aren't
> required to distribute their changes.
It was more that we wish to use the AGPL, to reduce the risk of somebody
refusing to make modifications available, because under the GPL they are
not required to do so, and the modified component is covered by the GPL
rather than the AGPL. Using the AGPL may give us a bit more leverage, if
the need arises.

There is a balance between enforcement and encouragement. On the whole,
I lean towards encouraging those who build public web services from modified
GPL software, to release the source code for their site under the AGPL, even
though the GPL does not require them to do so.

We probably could not enforce the AGPL for the reasons noted, but for those
visitors who care, it's a sign that "we play by free software rules for 
services."
> On the other hand, my reading of the FSF documents is that the
> source code your site would offer for download (containing
> PmWiki + PublishPDF + other components) could be licensed
> under the AGPL, even while PmWiki itself remains GPLv2.
> This is possible because PmWiki's license contains the
> "or any later version" clause of the GPLv2, which means that
> it can be treated like a GPLv3-licensed package and
> thereby be compatible with AGPL software.
Ah, I had not interpreted it that way, but I think you may well be 
right. If it's
OK to release pmwiki + our extensions in their entirety under the AGPL,
even though individual components are licensed under the GPL, then that
meets our requirement.

So the "or any later version" clause means we can choose to take the
pmwiki source under the AGPL, without pmwiki being explicitly offered
under the AGPL.
> So, someone downloads and installs the PmWiki+PublishPDF
> software, makes some modifications, and starts using it on
> a site.  You, as the package author, can request their
> modifications under the terms of the AGPL.  This would
> include any modifications being made to PmWiki itself [1].
> At that point we can figure out if we need any of those
> modifications merged into the upstream version of PmWiki
> and how to do that within the terms of the various
> licenses.  (Ideally the author would permit them to be
> used in PmWiki under the GPLv2 or some other compatible
> license, and/or provide a copyright transfer.)
I *think* we could require the author to make them available under the same
terms as the original component, i.e. GPLv2 or any later version. The only
reason the AGPL comes into play is that the software is providing a service.

AFAIK the only benefit of copyright transfer is when free software projects
use GPL v2 and omit "or any later version". In this situation, changing the
licensing terms requires the agreement of all copyright holders. The "or
any later version" clause gives the project owner the right to change the
licensing terms, e.g. to GPL v3, without seeking the permission of all who
hold copyright in the code.

So there is no additional benefit from a copyright transfer, and seeking
such a transfer may discourage contributions.
>> I do not think PmWiki ought to *require* use of the AGPL for public
>> hosted services, but perhaps this could be encouraged, and offered
>> as an option.
> I agree that PmWiki probably shouldn't require the AGPL.
> But if that's the case, I don't quite understand how providing
> an AGPL option would improve things, given that someone can just
> claim the GPLv2 source as the origin.  Maybe I'm just not seeing
> the benefit (to either PmWiki or its users) of the dual-license.
It's more that I had not understood the wording "or any later version" 
can be
applied to licences other than the GPL, and in particular to the AGPL. 
So we can
choose the AGPL, even though pmwiki does not explicitly offer it.

And should anyone ask why we use the AGPL whereas pmwiki itself uses the 
GPL,
I can now offer a reasonable explanation!

Thanks,
JR

-- 
John Rankin
Affinity Limited
T 64 4 495 3737
F 64 4 473 7991
M 021 RANKIN
john.rankin at affinity.co.nz
www.affinity.co.nz