Development of Creative Commons licenses

[Ali Baba <mail.alibaba AT free.fr>]

Hi all,

	I am building a wiki community and wondering what licence I should 
choose. Here is what I want to allow people to do :

« As long as you provide proper attribution:
- you are allowed to copy and distribute any article from this wiki to 
anybody and for any purpose (incl. commercial);
- you are allowed to modify any article on the wiki, and by doing this 
you agree to place your modifications under these terms.

If for non profit purpose, and still as long as you provide proper 
attribution:
- you still can of course copy and distribute any article from the wiki
- you can publish derivative works under any licence you wish to

If you have commercial purpose, you can only publish derivative work 
under the same licence as this one. »


	So if someone wants to use some articles from this wiki to write a 
book or a website, thay can either:
- make some modifications, and charge for their derivative work -- but 
they must then allow people to copy and modify it freely (i.e. 
CC-BY-SA, if I have well understood);
or:
- make some modifications, and retain all copyrights on their 
derivative works -- but then they must not take profit from their 
derivative work (i.e. CC-BY-NC, if I have well understood);
or:
- change nothing and redistribute whole or parts of it for any purpose, 
incl. commercial (i.e. CC-BY-ND, if I have well understood).

They are forbidden to:
- retain all copyrights on their derivative works if they want to take 
profit from it.
- "forget" to give proper attribution to original authors.

	Do I have to use three different licences to do this? And first, do 
they really express what I want people to do and do not?

	I have thought of one case that I find awkward. Let's say Tom takes an 
article from my wiki and publishes it on his blog with some 
modifications of his own. Following the terms of the licence CC-BY-NC, 
and since his blog is nonprofit, he does not have to share alike, and 
then he can choose any licence he wants. So he chooses to release it 
under CC-BY. Now George reads Tom's blog, find that he may copy this 
article and modify it for inclusion in a book he wants to sell without 
having to give the same rights to his readers.

	But by doing this, he is also selling a derivative work of my wiki for 
commercial purpose WITHOUT sharing it alike, which is what I want to 
prevent. The difference is that Tom has played a role in between. And 
maybe Tom is George's brother, and he changed only a comma... How to 
prevent this to happen? Or maybe, not having to share alike does not 
really mean that you are free to choose any licence?

        Ooh, I'm having a headache.

        Thanks for any help you could give to enlighten me.