These ebuilds come from https://github.com/anyc/steam-overlay.
If you have some problems, go to the official site first.
gobject-introspection : Introspection infrastructure for generating gobject library bindings for various languages ( http://live.gnome.org/GObjectIntrospection/ )
libappindicator2 : A library to allow applications to export a menu into the Unity Menu bar ( http://launchpad.net/libappindicator )
libdbusmenu2 : Library to pass menu structure across DBus ( http://launchpad.net/dbusmenu )
libindicator2 : A set of symbols and convience functions that all indicators would like to use ( http://launchpad.net/libindicator )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a steam
For Paludis use this rsync : rsync://gentoo.zugaina.org/steam-portage
If you have a problem : ycarus(-at-)zugaina.org