I heard during some NetApp training I took (not certain how authoritative my instructor was)that Data OnTap was a customized version of FreeBSD 4.x, which has long since been EOL. While I believe NetApp did contribute back some things to the FreeBSD tree way back in the day, I would guess they haven't in many, many years (but that's pure speculation on my part).
Quite the opposite, in fact. NetApp have contributed BHyVe (http://bhyve.org/ / http://wiki.freebsd.org/BHyVe), a full BSD-licensed Hypervisor, in the last year. They make regular contributions to several network card drivers and other low-level code. At least one or two FreeBSD committers are full-time members of NetApp staff.
