[pmwiki-devel] pmwiki licensing: AGPL option?

[Patrick R. Michaud]

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.

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.

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 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.

  [1] http://www.gnu.org/licenses/gpl-faq.html#AGPLv3CorrespondingSource

Pm