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

[Daniel Kinzler]

Brianna Laugher wrote:
[...]
> After rereading the CC-BY legal code it does appear you (and others
> who made this point) are correct, and I was quite mistaken about the
> strength of the CC-BY license.
> http://creativecommons.org/licenses/by/3.0/legalcode
> "You may Distribute or Publicly Perform the Work only under the terms
> of this License."
> 
> Indeed it seems CC-BY is already the "weak copyleft" I was thinking
> CC-BY-SA is... CC-BY is much stronger than I realised. I thought CC-BY
> just meant "include a byline with my name".

No it isn't, there is one important difference: derivative work, i.e. modified
versions. Again, compare to the LGPL: modified versions must be distributed
under the same license (though larger works which use/incorporate clearly
demarked LGPL components do not). This is not true for CC-BY: if i make a
derivative of a CC-BY work, I have to attribute the author, but i can license my
version under whatever conditions i like. That's not weak copyleft, that's no
copyleft at all.

> So, is this understanding correct: using CC-BY, a reuser could create
> a derivative work that was not freely licensed, but provide info that
> the source image was CC-BY (and provide link), and that would be
> acceptable? Is that true?

Yes, that is correct, but again, we lose the distinction of using/aggregating
works, and modifying them. I believe this is a very important difference (as
exemplified by the LGPL), and I maintain that an LGPL-Like CC license would be
useful - at least for me, it would reflect exactly what I, for one, want:

People can *use* my work *in* theirs, as long as they attribute me, but if they
*modify* my work, that modification must be freely licensed. This is stronger
than CC-BY but weaker (or rather, softer) than CC-BY-SA/GFDL (in their "strong"
interpretation).

> Well... now I think shoring up CC-BY-SA to be a strong copyleft is a
> good idea, since Greg is correct...if we can correct the
> misperceptions of people like me then I don't see why this idea
> wouldn't receive widespread support.

I think having a clearly strong/viral CC-BY-SA is just as important as having a
soft version. Of course, adding yet another license to the mix is not so great,
but I would hope that having *clearer* labels will clear up more confusion than
adding *another* label creates....

-- Daniel