We may say that evaluation is the same as the sellers (vendors) are presenting "the thesis for a Doctor's/Marter's degree" and "academic council member" (evaluator) from some "university" (forex-tsd forum) are giving some references to this thesis. If the evaluator is feeling that he is taking some responsibility (money responsibility for example) so he is having the right to refuse to evaluate. Or evaluator is having the right to ask for seller to disclose something. Or evaluator is having the right to make some agreement (if evaluator agree to evaluate something and but it will take some weeks for him as a job so the seller may to discuss with evaluator some kind of agreement...

Because will I evaluate just only one commercial proposal during the 4 hours every day for 2 weeks as a job? And as a results of good evaluation the seller will say to me: "good job! So, I see you like my EA so you can buy it for same price with everybody of course". I will not evaluate in this case. So, it may be the agreement sometimes. Of course it can be done without any "agreement" if the seller provides all necessary information to the evaluator. But I think in most of the cases they will not provide information in easy way. It is the responsibility of the seller to provide the information. No information for evaluation (forwatrd testing results and so on) - no problem: we can say 'not' to the seller or "cometo the next time when you will be ready to co-operate".

Because every case will be different.

Few days ago I refused to evaluate some EA. One Russian wanted to have evaluation. I was affraid that his EA is modified Terminator EA. I asked for the statement. He refused. I asked for EA's explanation. He said that even small explanaton is big secret. I asked for posts on any forums. He said that he never posted anything on any forums. I asked may be he knows someone (moderators of some Russian forums, some coders, some traders from Russia ...). He said that no one knows about him anything. I said that I need to know how it was coded. He refused. He sent just backtesting results only.
So, I said "Not" to him.
It was just one example.

Some people affraid that according to this evaluation many scams will come to the forum. But i am thinking/affraid in opposite way: according to this evaluation even some good proposals will be rejected.

So, evaluation is something like "community accepted" or "community did not accept in this time (timestamp)".