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There might be a special provision in Polish copyright law, that licenses may be repealed under very limited conditions regarding political or social convictions.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