Downloaded livedvd-amd64-multilib-20160514.iso can't be mounted as an iso image on a guest system with app-emulation/virtualbox-5.0.20. Error returned when trying to open/mount mentioned iso: "Failed to open the disk image file" / "Could not get the storage format of the medium". Latest image available at http://releases.gentooligans.com/ (livedvd-amd64-multilib-20160617.iso) works as expected.
This will be fixed with the next maintenance release.
This is now fixes in latest release.