ZFree was a free ISP that is no longer free.
(Warning - the following may not be 100% accurate, and may contain traces of nuts, but it's the truth as far as I know...)
Most people don't know that there was quite a bit of history behind ZFree. It was a result of Clear's (now TelstraClear) battles to provide telecommunications services in NZ. The local dominant ex-monopoly, TelecomNZ, forced Clear to sign an inter-connect agreement (which itself took years of court action and wrangling to get sorted) that had a clause saying that each provider would pay the other 2 cents per minute for a call originating on one's network and terminating on another. For example, if a Clear customer rang a Telecom customer, Clear would pay 2 cents per minute to Telecom. As the majority of NZ'ers (especially businesses) are with Telecom, this agreement meant almost every Clear call would attract this surcharge, - most of Clear's customers' calls would be to Telecom customers.
Then the Internet boom happened, and many many companies started getting many many phone lines put on - which Clear would sell to them for cheaper than Telecom would. And Clear came up with the rather clever idea of setting up a free ISP. Net result - hundreds of thousands of Telecom customers would terminate at a Clear number (ZFree) and stay connected for long periods of time. Still at 2c/min. (Most of these users didn't notice or care that their download rates were pretty slow). And the tables turned in Clear's favour.
Telecom NZ then tried to force ALL ISP's in the country to use the 0867 network, ostensibly so they could better control IP traffic, making claims such as too many dial-ups on the normal phone network could (conceivably) prevent others making 111 calls in emergencies. Any ISP who kept using the free (Clear) local calling numbers instead of the 0867 networkr would have their customers charged the 2 cents per minute directly. (And the customers would say "Why haven't you gone to 0867..." etc. This move was to try and stop their losses under the interconnect agreement with Clear, as Telecom felt they were gouging Clear "fair and square". Nevermind that these new charges were legally questionable under the "KiwiShare" arrangement.