I guess this statement on github says it all:
Offical ZFS on Linux [url='https://en.wikipedia.org/wiki/Dynamic_Kernel_Module_Support']DKMS[/url] style packages are available from the [url='https://tracker.debian.org/pkg/zfs-linux']Debian GNU/Linux repository[/url] for the following configurations. The packages previously hosted at archive.zfsonlinux.org will not be updated and are not recommended for new installations.
Since there are no zfs packages in Debian's wheezy repo, support for wheezy is done. This means zfs users should move to OMV 3.x.