I came across http://www.zoneminder.com/ in my quest to find an open source security system for the store. It has a bootable iso available making it a very easy install with a wide range of supported cameras.
From the site:
"ZoneMinder the top Linux based video camera security solution. ZoneMinder is intended for use in single or multi-camera video security applications, including theft prevention and child or family member or home monitoring and other care scenarios. It supports capture, analysis, recording, and monitoring of video data coming from one or more video or network cameras attached to a Linux system. It is suitable for both do-it-yourself and professional installations."
If your looking for a modern digital security system this may be your ticket.