To recap from your post over on Applefritter:

http://www.applefritter.com/node/21411

You asked about MacADT, though that's not what you really wanted, as you found out later. But for those that do:

I updated MacADT as part of the older DOS ADT package so that it will support IIgs computers in the first place; it wouldn't ever have worked with the version you had. The updated DOS ADT package is on the ADTPro download page:

http://sourceforge.net/project/showfiles.php?group_id=170262

MacADT includes a server that will run on a 68k Mac.

Newer Macs that run OSX can use ADTPro, which expands on ADT in a bunch of ways, including supporting all the different devices that you can connect to the IIgs. The ADTPro server is in Java, so you aren't constrained by Classic. And the ADTPro server will serve both DOS ADT as well as ProDOS ADTPro down on the IIgs.

The ADTPro website has a pile of setup and bootstrapping information:

http://adtpro.sourceforge.net

And an entertaining walkthrough is here - "Using an Apple IIe as a serial term with Gentoo Linux":

http://www.dataswamp.net/apple2eserialterm/

- David