Dwight:
From page 71 of the PlotMaker 2.2 Reference Guide (with ArchiCAD 6.5). I think this is how they also dealt with HPGL in earlier versions: not a dedicated driver, but by using a specific plotter driver.
HTH
David
Plotter Manufacturer Not Listed
If the manufacturer is not listed with any model, check the user
manual of the plotter for compatibility and emulation modes. If the
plotter accepts HPGL, HPGL-2, DMPL, BGL or PCI data, there is a
good chance of making it work.
Configure the plotter to one of the graphic languages shown in the
following table (the order of the list below is important. We
recommend using the earliest applicable language for your plotter):
...
HPGL Generic HPGL
(Hewlett-Packard standard) (plotter origin: bottom
left)
HP 7885A DraftMaster I
(plotter origin: center)
...