/netbsd: SUNW,bpp at sbus0 slot 4 offset 0xc800000 level 2 (ipl 3)
   not configured
   
   Is it a parallel port?  Is there a simple way to get it configured
   and useable?  Does a driver need to be written?  If so, does anyone
   have some docs on it?

yes.  yes/unknown.  it is written, but not really well tested.
look in sys/dev/sbus/bpp.c ...
   
   I have a pc532 with 8 serial ports, but I can convert 2 of them
   into parallel ports.  I'd like a bit more speed between the two
   machines, and thought this might be a simple solution...

sounds like a good idea.  and the sparc port would benefit from it
a lot, too.. :-)