Are they related to your website's topic? Do they still have the same content they were listed with? It would help if you'd tell us the domain names so we can give you better advice.
Depends on you... If you have no intrest in them its going to be very hard to develop or maintain it.
We need to know what they are in order to comment... Actually it doesn't matter - an automated tool removes expired domains and they are manually checked before they are restored. If they are still listed then it is probably because the systems are down at the moment and running on an old backup copy. The probability is that you have bought some formerly listed domains; worthless.
If they have a pr4 and above, I think you can sell them. Or if your current website is not listed in DMOZ and rankings in SERPs are not good, move the content to these domains.
You can sell them. DMOZ would not know. Yes, if you don't have any site listed in DMOZ move your content in one of the domains and you have a DMOZ listing.
Remember he said they were expired domains - you know there is an automated tool that moves expired domains out of the main directory. So there is a very strong probability the only reason they are showing is because DMOZ is currently showing an old backup copy. I don't think he has anything worth anything for DMOZ value.
If it has a high PR, like 4 or 5 just resell it. Well, but if you already have a concrete plan on how to develop in that do just that.