Richard, the link you provided is for the Windows version, but he is asking about the CentOS (Linux) version, which (from what I can tell by the tech bulletins and deployment guides) is now a component of Server Edition. Basically, the Linux version of Voicemail Pro and One-X Portal runs on Server Edition core, even if you don't have licensing for Server Edition. To install, you boot into Server Edition installation and select "Application Server" mode. Server Edition is only supported on a dedicated server, or on VMware.
And please tell me if I'm wrong! I've been trying to find a good upgrade path for older versions of Application Server that are already running on Hyper-V. Booting from the installation DVD or ISO in Hyper-V results in a kernel panic, and upgrading via RPM upload to the existing installation has been problematic.