I need some help 

Hello, I see you are a custodian, saw your message on the fair use issue. I am in the middle of negotiating with a photographer for a free license on an image posted previously as a fair use item. He wants it to be in Wikipedia but there is a language barrier and he needs help understanding what his choices are. I am worried am going to explain it poorly to him. He is from Switzerland and asked me to keep it simple and short how I explain it, not send him a link to a legal manual. Can you help me? I am conversing with him via email. I do not want to post his email address publicly here unless I get his approval. If you want to talk to me in email about this, my email address works in my box here. It is about an image Chowbok tagged and an additional one as well so I don't want to delay explaining the licenses to this person. I don't want him to be confused. He is a professional. I want him to understand well enough that he even opts not to license it if it is not best for him. We could try to get something else if it is not the right thing for him. But I think he would like to do this if we can just help him understand. What protects his photo credit best? GFDL? CC BY SA? Also, the GFDL mentions in the text that someone copying 100 copies or more must be given the source code, which is meaning a software package. For a photo, I hope the "source code" would not be any greater image than what he gives us to put in Wikipedia. He may even decide to give us a bigger image than what we have up currently. I am in the middle of trying to answer this photographer and am worried I'm going to write something he won't understand or that's too long. –