GPLv2/v3 compatibility?

Richard Fontana fontana at sharpeleven.org
Fri Jul 20 02:15:00 UTC 2012


On 07/18/2012 11:53 PM, Ted Ts'o wrote:
> On Wed, Jul 18, 2012 at 10:40:38PM -0400, Richard Fontana wrote:
>> Currently, vanilla
>> copyleft-next is incompatible with {copyleft-next + dl-supp} and
>> {copyleft-next + ws-supp} (much like "GNU GPLv2-only" is
>> incompatible with GNU GPL3) (i.e. there's nothing corresponding to
>> GPLv3/AGPLv3 cross-compatibility), though this is just because I
>> deferred thinking about whether there should be compatibility or
>> not.
> 
> In this last sentence, are you referring to the question of whether
> vanilla copyleft-next could or should be compatible with GPLv2-only,
> and/or what the compatibility of copyleft-next + dl-supp could or
> should be with respect to GPLv3?

I was probably conflating two thoughts there. In part, I was thinking of
compatibility between vanilla copyleft-next and copyleft-next + dl-supp
(or ws-supp), as though GNU GPLv2/v3 had never existed. For example, A
starts a project using vanilla copyleft-next as the license. Should it
be possible for B to license out a derivative work under copyleft-next +
dl-supp or should that be disallowed? There are decent arguments on both
sides.

It relates to the issues of GPLv2-only / GPLv3 compatibility in the GPL
universe, however. In fact, what was going through my mind was the
reaction (back in ~2007) some had to the argument, coming from FSF/FSF
counsel/FSF advocates, that those who objected to the anti-Tivoization
provisions could always use the "additional permissions" scheme
explicitly laid out in GPLv3 (note btw that I've deleted all that as
unnecessary obvious stuff and possibly even something that shouldn't be
encouraged). Since, in the additional permissions scheme, additional
permissions are explicitly removable downstream, anyone could transform
a GPLv3 + "additional permission to ignore anti-Tivoization clauses"
into standard GPLv3, and some found this objectionable on policy
grounds, because they didn't like the idea that a downstream licensee
could impose a more restrictive license than they themselves had chosen
upstream.

For the moment, I've conveniently avoided the related problems of
compatibility between copyleft-next and the GNU GPL license universe by
putting in the clause that magically allows any copyleft-next flavor to
be relicensed under GPLv2 or GPLv3 or AGPLv3 or later. But they raise
the same policy issues, or seem to.

I wonder in fact if dl-supp serves any purpose if one can relicense
under GPLv3. I deleted the more obscure contractor/outsourcing clause
(see http://www.gnu.org/copyleft/gpl.html#section2 second paragraph)
with the justification being that any company that cares so much about
clarity on this issue can always avail themselves of relicensing under
GPLv3 (of course this argument disappears if one removes the relicensing
clause). I feel somewhat differently about ws-supp but that's another topic.

  - Richard


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