As talked with lejonet, upstream stopped developing it, it's not used by anything in the tree and he wants it removed ;)
commit 05f45a3bdc1307f770d47b0528cf854239b9796f Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Sun Jun 26 17:01:39 2016 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sun Jun 26 17:01:39 2016 dev-libs/hammer: Remove last rited package