Some people just feel that saying "no" is a form of confrontation because its delivering what in their minds is bad news. And rather than saying it, which might make them uncomfortable, they feel it necessary to deliver it in what they deem a more forgiving manner.

I have a friend I've known over 50 years and he almost never says no when he has to turn things down. He will say, " Lets see how it looks when it gets closer and I'll let you know." Which is an entirely different answer from when he wants to do something. So while I never get "no" directly , I've come to understand what his version of "no" is and don't give it any more consideration when I hear those deliveries.

Its a kind of an unspoken understanding and perhaps that's what you should do with this person.