Orphaned ( aka maintainer-needed ) packages, are those that nobody, neither a maintainer nor a herd, is looking after them. Such packages oftet get removed from portage because either they don’t work anymore or there are just too many open bugs and nobody really cares about them.
Recently the TreeCleaner Project, as a decent way to inform everybody ( both devs and users ) about packages that are candidates for removal, introduced a new package to track them.
If you want to proxy maintain one of them, just send an e-mail to gentoo-dev mailing list and who knows, maybe a dev will pop up and work with you :-). If you haven’t heard about proxy maintainers before just take a look here and here.