[cc-licenses] Most important feature: GPL-compatibility

Francesco Poli invernomuto at paranoici.org
Fri Dec 30 06:22:10 EST 2011


On Thu, 29 Dec 2011 20:08:30 -0500 Anthony wrote:

> On Thu, Dec 29, 2011 at 2:57 PM, Mike Linksvayer <ml at creativecommons.org> wrote:
> > One of the reasons some form of
> > BY-SA->GPL compatibility is interesting is that some want
> > source-requiring copyleft for non-software,

I personally think that a work is not really Free, without source
availability.
Therefore, a strong copyleft mechanism has to require making source
available.

> > it isn't reasonable to
> > make source requirement for all BY-SA use,

I instead think it would be reasonable, but that's the topic for a
different discussion...

> > nor is it reasonable to
> > create another incompatible copyleft pool.

This is the key point: the CC-by-sa license currently creates a
distinct "copyleft pool", incompatible with the one created by the GNU
GPL.
That's a real issue that should be fixed as soon as possible.

[...]
> Why not a CC-GPL, which is (one-way) compatible with GPL?

The CC-GPL is just a re-branded GNU GPL, as far as I understand it.
It does not solve any incompatibility issue, since it's itself
incompatible with CC-by-sa and with CC-by.

> 
> One of the advantages of CC-BY-SA compared to GPL is that it *doesn't*
> have the sometimes onerous requirement to share source.

I see that as a bug, rather than a feature.
It's a weak copyleft, from this point of view.

When source (the preferred form of a work for making modifications to
it) is not made available by the author, each recipient finds
himself/herself in a position of (technical) disadvantage with respect
to the author: the author has the possibility to make modifications
that the recipient cannot make as easily.

> 
> Something to keep in mind is that the "source" of a CC-BY-SA work (the
> preferred form for making modifications) might in some cases be
> thousands of times bigger than the non-source version of the work.

In those cases, maybe that form is not really preferred over other
smaller formats. Maybe even the upstream author prefers to keep the
work in some other more "space-efficient" format.
When this happens, the smaller format is the actual source (namely, the
preferred form for making modifications)...

There may be some difficult corner cases, but please keep in mind that
the definition of source proposed by the GNU GPL is often flexible
enough to address most cases without problems.


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