Garryts: my mac at home is under OSX server
The network render will need a monitor to be install, because it request a serial, as the serials used by various plugins if you own some of them. But once launched, I don't know if it need a video card or not (I don't think so..)
Contact the Eovia tech support about this, they will be able to answer you a lot better than me
(support (at) eovia dot com)