These ebuilds come from http://hg.nxtoo.org/hg/nxtoo/nxtoo-overlay/.
If you have some problems, go to the official site first.
virtualbox-modules : Kernel Modules for Virtualbox ( http://www.virtualbox.org/ )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a nxtoo-overlay
For Paludis use this rsync : rsync://gentoo.zugaina.org/nxtoo-overlay-portage
If you have a problem : ycarus(-at-)zugaina.org