I believe Wayback's policy is to duplicate unless explicitly denied (via robots.txt) or through request.
I think it's safe to say that since the original site owner let the original site disappear, that the owner has lost interest. As long as the presented information is credited properly and the source is correctly noted I think it should be replicated elsewhere. If the site owner comes forward and objects to his information being up, then it's a simple matter of taking it down. The same thing the Wayback people would do.
Normally, I would abide by the same policy as you. However, I recognize that sometimes, it's better for the whole to simply break the rules now and ask for forgiveness later. As long as no money is profited from his/her hard work....
