[Foundation-l] [Commons-l] Requirements for a strong copyleft license

[Gregory Maxwell]

On Dec 2, 2007 9:24 PM, Fred Benenson <fred.benenson at gmail.com> wrote:
> Question for the lawyers here -- even if we *wanted* to add stronger
> copyleft to a CC license, say creating CC-BY-SA+, could we?
>
> Isn't the whole problem here that the licenses rely on the various
> definitions of "derivative works" for different mediums?
>
>  That is, the GPL can have strong copyleft because including source from
> other GPL works into a new work necessarily creates a derivative work, and
[snip]

I write copyrighted work X. You create and distribute a new work, Y,
which includes X.  Because your work *includes* my work you are
subject to the copyright-related restrictions and obligations related
to the distribution of my work.  Without a license (or fair use...),
your distribution is a copyright infringement.  I may offer you a
license which contains many types of requirements which must be met in
order for the license to be valid.   End of story.

It is sometimes interesting to ask if work Y is still encumbered by
X's copyright obligations even if X is not directly included (for
example, what if Y was a translation of text X into another language).
 In these cases you might actually have a complicated issue on your
hands, although not generally for a translation.  The case law on
these matters is idiosyncratic and very dependent on the type of work
in question. But this is not generally the question of interest when
we discuss copyleft licenses for photographic works or audio
recordings.

Issues like this common confusion about the role of 'derivative' works
with respect to copyleft are part of the reason why GPLv3 uses novel
language (with internal definitions) to describe many concepts
('propagate', 'convey', etc).