LibreSSL is already in Gentoo, but still requires a lot of ebuilds to be fixed. This overlay serves as a testing ground and makes testing easier by providing an openssl dummy ebuild, so you can compile packages against LibreSSL which don't have the 'libressl' USE flag yet.
With paludis: see Paludis repository configuration
With layman:
layman -f -o https://raw.githubusercontent.com/gentoo/libressl/master/libressl-overlay.xml -a libressl or layman -a libressl
