[Zope-dev] ZPL and GPL

[Michael R. Bernstein]

On 25 Jun 2001 10:26:10 -0400, Shane Hathaway wrote:
> According to management, there's a zope-license list somewhere and we
> expect to move to a GPL compatible license. Paul says:
> 
> "I think the goal should be for Zope and Python to converge on the same
> license, with perhaps the new license being some off-the-shelf license
> like Apache's."

Hmm. So a BSD style license, then. Are there currently any Zope-derived
distributions that are proprietary (third-party or DC's)?

If not, does DC anticipate there being this kind of third-party
proprietary derived distribution in the future?

Other than keeping the door open for this eventuality, is there any
other reason to choose a BSD style license over the GPL?

As I see it, BSD style licenses ensure that anyone can make proprietary
derived distributions. They are very similar to public domain in this
regard.

The GPL ensures that no-one can make proprietary derived distributions,
except that the copyright holder always has the option of releasing
under another license if they wish, so dual licensing or changing the
license is always an option *if you have contributors assign the
copyright of their contributions to you*.

NPL (Netscape Public Licence) style licenses try to make it possible for
no-one to make proprietary redistributions *except the original author*.
The license generally requires contributors to allow the original author
to make proprietary redistributions using their contributions even
without copyright assignment (or that assignment is implicit in the
contribution). Note that re-licensing (or dual licensing) would still
require contributors to assign copyright just as with the GPL.

Given that DC is the copyright holder for Zope, they would do well (IMO)
to consider relicensing Zope under the GPL or LGPL, as that would force
anyone who wished to redistribute a proprietary version of Zope to
negotiate a separate license with DC, actually strengthening DC's
position in that regard, while generally ensuring that contributors work
would remain GPL.

If some contributor did not wish to let DC relicense their contribution,
they could simply not assign the copyright to DC. DC has the option of
not adding the contribution into the distribution, or of removing the
contribution from any relicensed version.

So. The current ZPL is essentially a BSD style license with the optional
attribution clauses, and a mandatory advertising clause (although
there's an escape hatch too). It seems that the mandatory advertising
clause is most applicable when someone creates a proprietary derived
distribution of Zope. If there are none such (I'm not aware of any),
then the clause is unneccessary.

Unless I've misunderstood something (which is certainly possible), DC
doesn't seem to have anything to lose by switching from a BSD style
license to the GPL (or a GPL style license with an additional optional
attribution clause), and quite a bit to gain.

Note that this is a different option than merely switching to a BSD
style license that is 'GPL compatible'.

Michael Bernstein.