The problem is primarily hardware. The Agfa Accuset 800 is a host-based system that requires a card to be installed in your computer as you can see
here. For the least expensive system, they
give you the computer!
When you send a job to the Accuset 800, you don't print to a hardware PostScript printer. You print to a software PostSript RIP. If you were printing to a hardware PostScript printer, the printer's PPD file would be compatible with virtually every version of every OS for which a PostScript driver was available. Unfortunately, software RIPs are OS and RIPkit-specific.
The bottomline is that there is no cheap upgrade path to MacOS X.