Nessus review by PC Magazine: "Based on a client/server architecture, Nessus lets users run the administrative console, which executes vulnerability scans and holds databases on a machine other than the ser".
I personally think PC Magazine was dismissive of Nessus. These magazines tend to be biased against the non-Windows platforms. I have not done so myself but one can write one's own security scans via the Nessus plug-in language (NASL) and there is at least on Perl module available to programmatically control Nessus. My employer has built a Linux, Apache, PostgreSQL, and Perl based vulnerability assessment application around the Nessus security scanner.