As far as I know, original content, that is content researched and posted, remains the intellectual property of the author. That's why I've limited myself to moving my own articles over from the old Forum. It would be wise, I think, to be careful about lifting stuff from the old Forum using the Wayback Machine unless you wrote the original article on there yourself.
I think if you can't get permission from the original author, by all means credit them, but I may have to take it down if I get any complaints.