As a person who lived in New Jersey for over 40 years before moving to Florida and who used/uses EWR I can tell you that there is Wi-Fi available in all of the terminals but by no means is it free as far as the public areas are concerned. The current incarnation of the service is operated by AT&T (Formerly Wayport) and as I recall the fee is $4.95 for 24 hours for connection to a single location, in other words that 24 hours only applies to the AT&T Wi-Fi service at Newark Liberty International Airport and not anywhere else, so if you wanted to connect to an AT&T Wi-Fi hotspot at your arriving airport or at a Starbucks for example you'd have to pay another $4.95 for that location. There is an upside though, if you are an AT&T Broadband customer the Wi-Fi access is included as your part of your broadband package and you will be able to connect to multiple locations at no charge and I believe this is the case also with qualifing Verizon FiOS Internet customers who have the Wi-Fi connect software installed on their laptop.
Another option if you are on a First Class flight or are a paying member or guest of one of the airlines private clubs you will have free internet access inside of the club but as a caveat it has been my recent experience that airlines lke American, Delta, Continental and United have started instituting the use of a password system on their wi-fi connection welcome page to prevent leeching from outside of the clubs doors by common folk such as myself who can't afford a membership or flying first class.