There is a site called moviechat.org that claims to have archived all the posts from imdb boards. I looked up Sister Wives (it is easy to search, so a good feature), and the look of the page is exactly like imdb. However, none of the posts were there. It looks like it is the work of one guy and he is asking for donations. I don't know how legit it is.
After reading your post I went to that discussion area and I'm not too sure this guy knows what he is talking about. First, I don't believe anyone at IMDb told him 'message boards are of absolute minimum value/concern to the company, and it is highly unlikely that the company would pursue any legal action should someone attempt to archive the boards'. First, why would he want to archive the board messages? Replicating the boards is all that we need. Plus he said he used to be a lawyer. He is as literate as our president. Also, why does he need money? What is he using that costs money? Does he want people to pay for his time? However, none of that is our concern. I'll post if other people post there and I definitely want to see the posts he archives. I think the donations are for a lawyer, a real lawyer.