If you get right down there are a lot of things about copyleft that are untested in most legal regimes around the world.
A related issue to the one Artur raises is that many legal systems have an absolute right to withdraw contractual offers if they have not already been mutually agreed upon. If you believe that a copyright license is a form of contract (which is probably true in at least some jurisdictions), then it is likely that the licensor can stop offering a copyleft license to new parties, even though they can't revoke it from any existing users. If a jurisdiction allows the license to be removed from future uses (all the language about "perpetual" notwithstanding), then that opens the door for all kinds of headaches for downstream users that weren't already using the image prior to the license withdrawal.
Obviously, this is just one kind of ugly scenario, but issues like this will eventually have to be confronted as the copyleft movement continues to stretch copyright law beyond the limits at which it was originally conceived.
Personally, I'm optimistic that the letter of copyright law will ultimately be able to play amicably with the concept of copyleft, but we will have to see.
-Robert Rohde
On Tue, Aug 5, 2008 at 5:03 AM, Henning Schlottmann
<h.schlottmann@gmx.net> wrote:
Artur Fijałkowski wrote:
> I don't know how it's in other countries, but in Poland copyright act
> says that author ALWAYS can withdraw license.
Are you really sure about that? Because it would be a violation of every
principle of copyright. Licenses can be limited upfront to terms, but an
unlimited license - such as our GFDL or our cc-licenses, are
irrevocable. Everywhere, including Poland.
There might be a special provision in Polish copyright law, that
licenses may be repealed under very limited conditions regarding
political or social convictions. But in that case the author has to pay
damages to any legitimate publisher of the work.
A revocation on the spur of the moment because someone doesn't like the
project anymore is not a legal right and we should decide how to deal
with those cases.
Ciao Henning