sys-apps/openrc currently has a USE flag to control whether capabilities are supported by start-stop-daemon and supervise-daemon. Making this feature optional makes very little sense. It means init scripts must be written to account for the possibility of missing capabilities support. See bug 939471 as an example. I think libcap is a very lightweight dependency. Please consider enabling capabilities support unconditionally, at least in Gentoo.
This is fixed and will be released in 0.56. Thanks, William