youtube-dl : A small command-line program to download videos from YouTube. ( http://bitbucket.org/rg3/youtube-dl/ )
zsync : Partial/differential file download client over HTTP which uses the rsync algorithm ( http://zsync.moria.org.uk/ )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a zugaina
For Paludis use this rsync : rsync://gentoo.zugaina.org/zugaina-portage
If you have a problem : ycarus(-at-)zugaina.org