The HP 6 is a PostScript printer, and is supported by OS 9 or X with the PPD.
On the D-Link page the footnote says:
1 Printer Server software included is for Windows Operating Systems only. Postscript Level 1 and 2 printers can be connected to the DI-704P for Macintosh OS 9.x or X computers. The DI-704P does not support non-Postscript printers with Macintosh OS.
So it sounds like it should work. You are printing to the print server in the router. The
printer does not have an IP address in this case. Use the router's address. If the router has a way to turn on AppleTalk, that would make it visible in the Chooser.
To create an IP printer in OS 9, use the Desktop Printer Utility, found in Applications:Utilities. Create a new Desktop Printer, select LPR, select the PPD for the HP 6, enter the IP address of the router, and the name of the queue, (LP?) and clcik Verify to test. Save it when it works.
