That is merely an IP phone. You need an IP PBX backend for that to plug into. You can roll it yourself with Asterisk, you simply get analog interface cards to slap into the server you're going to use.
http://store.digium.com/telephony_card_selector.php
It's a fair pain in the arse if you don't know what you're doing though - how much do you value your time? Because once you take into account the back end, and 6 to 8 of those phones, you're soon up at the level where you can just get a vendor in. We just redid our PABX at work the end of last year, $2500 or so on education special for a 4 CO/8 extension system with voicemail. Only two new fancy system phones included in that, and it's only 'VOIP Ready' but yeah.