http://www.firebirdsql.org/en/firebird-3-0/ has been released in April 2016 please bump. Thank you.
>=app-office/libreoffice-5.3[firebird] is going to depend on this: https://cgit.freedesktop.org/libreoffice/core/commit/configure.ac?h=libreoffice-5-3-0&id=ddc57a6915ed06ecbf2e89e8003e73a604fd4324
Current release is Firebird 3.0.1 and provides cmake buildsystem, this should definitely be looked into to produce a saner ebuild.
I found http://data.gpo.zugaina.org/linuxunderground-overlay/dev-db/firebird/firebird-3.0.2.32703.0.ebuild
Bumped, please test.