It is very possible that the owner has a recurring payment in place, or that the owner renews after it expires. Because GoDaddy gives a redemption period like all registrar, many domain name investors will actually allow their domains to go through auction to see what the “market value” is of a domain name and THEN renew it. It sucks if you’re the buyer thinking you won the auction. It happens often, unfortunately.
When searching from keyword DHG will take your list of keywords and search each one, the pages will then be crawled to find unique domains to check availability of. The process is relatively simple but very time consuming when done manually or semi automated as was necessary in the past. Luckily now the job can be set and left to work while you do something else.
Here's an old post on search engine roundtable that claims google's policy is to discount previous backlink juice when a domain changes ownership. I'm not convinced whether this is actually true or something Google says to discourage excessive domain buying / 301 redirecting for SEO benefit. The comments above seem to give varying opinions on this matter. Would be great to get to the bottom of that one!
Referring domains for anchor phrases usually reveals similar information. What you really want to look out for is whether or not the site has been picked up by a spammer in the past. A lot of times these expired domains were dropped, picked up by a website owner who then tried to rank it for keywords like Viagra, Cialis and whatever. You obviously don’t want that kind of domain.
The way this list is implemented means I can't update prices, nor removed sold domains automatically and sedo doesn't provide me with the tools I need to implement it properly. Unfortunately some users keep contacting me to update their domain prices or remove their domains and I can't keep doing that manually. So I've decided to disable the list for now.