Well, I got this working after a lot of hassle but it works just fine. The Zterm solution I have tried but I was done with zterm as soon as OS X PB was released.
1) Do not download Zterm, just use the terminal application which comes with OS X (under the Applications folder)
2) Purchase the keyspan adapter (USA-19 or the dual if you want)
3) Download the drivers for OS X and install them
4) Make sure you have the developer tools installed (gives you GCC, etc)
5) Download consolse server software from <A HREF="http://www.conserver.com" TARGET=_blank>http://www.conserver.com</A>
6) Compile and install conserver on OS X (./configure ; make ; sudo make install You may need to tweak compiler settings)
7) Then create a configuration file that maps the name of the device to your console
a) default install for the configuration is /usr/local/etc/conserver.cf
b) Put a line in conserver.cf like this (on a line by itself):
routera:/dev/tty.KeyUSA19191.1:9600p:&:
if there is more than one keyspan device add another entry:
routerb:/dev/tty.KeyUSA1813.1:9600p:&:
The OS X will dynamical create a device in /dev everytime you plug in the keyspan device so as long as you always plug it in the same port you should have the same device number. It's actually really cool to setup you conserver.cf just plug in the keyspan (after the drivers are installed) and type cd /dev ; ls -l and you'll see the tty.KeyUSA*** device
After you conserver.cf is setup start console server using the script that's also in /usr/local/etc, the conserver.rc:
conserver.rc start or
rc.conserver start (depending on what you call the type.
9) Then after conserver is started, simply run the console program (make sure it's in your path) from the command line:
a) /usr/local/bin/console routera
b) for me it asks the root password for some reason, haven't figured out why. It might ask you for your own password
c) There are other options to 'console' as well, like console -u (show users) or console -x (examine ports and baud) or console -h for help
10) Remember that everytime you reboot your Mac the consoleserver needs to be restarted!