Multipath HA for disk access on a NetApp Active/Active cluster can be installed without any additional licensing. The Data ONTAP Active/Active Configuration Guide (http://now.netapp.com/NOW/knowledge/docs/ontap/rel73_vs/pdfs/ontap/aaconfig.pdf) lists the requirements for configuring and cabling this feature. Please refer to page 147 of the guide.
It is a best practice to use Multipath HA for every disk loop.