It's one link and the search engines don;t use it any more, on 2003 it was great as Google and Yahoo and a few others used it as a base
DMOZ can give huge boost, I can't believe I read some posts saying that DMOZ is crap. There are some providers who can submit & approve a listing in a fraction of time.
I haven't tried it but I have talked to a moderator online before and he told me the quickest way to get inside is to become a moderator. You apply to be a moderator and don't tell them the whole purpose is to put your site in and then you put your own site in DMOZ. Moderators are broken down by categories so you need to apply for the category you want to put your website in. Most moderators have sites in the category they are moderating and they pretty much have the monopoly on who they let in or not.