You mentioned a program that ran on your UNIX account in college to provide an “ad-hoc ISP connection.” I wonder if you’re thinking about “term,” a program to allow shell account users without SLIP/PPP access a way to put their home computer on the network, in a sense. It’s described in this article from 1994:
I have fond memories of trying to figure out all the troublesome characters to escape when trying to run term over a series of terminal servers, hosts, and telnet connections. 🙂