An excerpt from "The Brain Makers" by HP Newquist (pg. 196):
Before long, Symbolics officials claimed that Stallman was actually taking the code that they were giving back to the lab, and that he was forwarding it to Greenblatt. Symbolics hackers even monitored Stallman's activities by using a little known feature that enabled networked LISP machines to watch what other LISP machines were doing. In essence, a hacker on LISP machine A could literally watch the screen activities of LISP machine B. After a few of these spying sessions, it became clear to Symbolics that Stallman was forwarding LISP code to LMI.
Several Symbolics executives approached MIT's administration and presented their evidence. Do something about Stallman, Symbolics' executives demanded. In order to keep its relationship with Symbolics on an even keel, MIT warned Stallman to stay away from the various LISP projects, but stopped short of denying him access to the lab's computing facilities. One more infraction, however, and Stallman m