in fact it's only legal problem european law say one can't abandon his moral against a text, except 50 years after his death, 70 years in France, so CC0 can't be choosen
anyway we're looking if there's any problem to go to a less restrictive licence such as CC-BY, we will be sure at the end of the week

*his moral right
that means globally that we must attribute works of contributors, as we're based in europe and a major part of contributions (except takana corpus original sentences) after some internal discussion we've realized that maybe CC-BY can be used, as Tatoeba MUST attribute works, after if people want to reuse the contributions without attributing it to original contributors, that will be their problem (in fact no problem as long as they don't reuse without attributing sentences or corrections from european contributors or other countries where public domain is different from US definition)
so the licence is only to make things clear

by the way, we wouldn't have take a long time to choose a licence or so if there were no threats nor possible juridical problem, I far prefer coding than looking into law books

the content will now be licenced under CC-BY 2.0 FR, which is for the moment, the less restrictive we can do according to european law