Yes online poker is definitely legal in New Zealand. Refer Department of Internal Affairs Gambling Act 2003, Fact Sheet #27 (you should be able to google it). This Fact Sheet covers "remote interactive gambling", there is another Fact Sheet about poker, but that is mainly guidelines for pubs running tournaments.
As far as the tax status, see
http://www.stuff.co.nz/national/4910...x-a-shady-area
for example. It doesn't look like the IRD sees online poker income as causing significant "leakage" from the tax base and there is basically no will to enforce the legislation.
It is hard to get across how much of a non-issue this is politically in New Zealand. There are gaming machines here, but the numbers are capped and I would say that gambling is seen as less of a problem than in Australia. Any anti-gambling sentiment is usually focussed on gaming machines as they are seen as sucking money out of poor communities.
Also relevant: the Auckland casino recently applied for an internet gaming license (not sure if that included poker) but that was emphatically turned down. Since the existing government is looking likely to be re-elected in November the status quo for online poker should remain through to 2014 (not that any other party actually has alternative policies on online poker; no-one has any poker policies).