GPLv2/v3 compatibility?

Ted Ts'o tytso at mit.edu
Thu Jul 19 03:53:53 UTC 2012


On Wed, Jul 18, 2012 at 10:40:38PM -0400, Richard Fontana wrote:
> I removed the so-called 'anti-Tivoization' provisions of GNU GPLv3
> section 6 out of vanilla copyleft-next and into a separate document
> currently called "dl-supp". I also added a separate document called
> "ws-supp" containing substantially similar text to the first half of
> the GNU AGPLv3 section 13. I don't think I really explained this in
> the commit logs so I'll go into that a bit here. The idea is that
> the vanilla version of copyleft-next won't have an 'Affero clause'
> (much as GNU GPLv3 doesn't) and, unlike GNU GPLv3, it won't have
> 'anti-Tivoization' provisions. Only the *initial* licensor (someone
> who's starting a new work from scratch) can choose to supplement
> copyleft-next with one of those "supp" documents. 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 wasn't sure whether I was parsing it correctly, since this was
something I immediately started thinking about when I started reading
this paragraph, and I wasn't sure whether I was projecting my thinking
onto yours.

In any case, the question of compatibility as a goal with GPLv2 or
GPLv3 is a very interesting one.  On the one hand, the ability to take
code from one project and reuse it somewhere else without being
unnecessarily limited by licensing compatibility issues is obviously,
highly desirable.  (For example, since e2fsprogs has two files which
are lifted straight out from the kernel, there's no way I could ever
take e2fsprogs GPLv3 due to its anti-Tivo clauases, regardless of
whether I wanted to or not.)  On the other hand, licensing
compatibility of necessity constraints what you can put in the new
copyleft-next license.

Regards,

					- Ted


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