In regards to their RSS feed, I would imagine that you'll still be able to see it. In fact you should be able to read the site but just not post anything since you won't have a profile. I guess they could make it also a read only site if a person has a membership and then the RSS wouldn't work but that would be kind of a wrong move in my opinion.
I don't know about that. I have a referral link from another Ning group, and just tried to access it. The page was blocked, and I needed to sign in to see it; when I tried to register it asked me for $10.
My guess is that unless you're registered, it won't let you view anything. I'd expect it would impact the RSS too. I agree it's the wrong move, but they may not have any choice depending on how Ning is set up.