In 1983, Jennings created the Fido program, which spawned FidoNet,[1] the first message and file networking bulletin board system (BBS).

[2] Aside from creating the protocol for networking BBSes, Jennings: built Wired's first internet presence; wrote the portable BIOS that led to Phoenix Technologies BIOS, contributing to on MS-DOS integration and interoperability;[1] ran an early regional internet service provider – The Little Garden (later incorporated as TLGnet, Inc);[3] and maintains an informal archive of Cold War science and technology.

From 1988 until 1991, while he lived in San Francisco, Jennings was the publisher and co-editor, with Deke Nihilson, of Homocore, one of the earliest Queercore zines.

The name came from the pages of J.D.s zine, and featured musicians and writers such as The Apostles, Steve Abbott, Donna Dresch, Larry Livermore, Daniel Nicoletta and G. B.

[3] The co-editors' other activities, such as organizing Homocore shows where bands such as Fugazi and Beat Happening appeared, and writing for and creating other publications, helped popularize the Queercore movement in the United states and internationally.