Jon "maddog" Hall is the Executive Director of Linux International, a non-profit organization of computer vendors who wish to support and promote Linux-based operating systems. The nickname "maddog" was given to him by his students at Hartford State Technical College, where he was the Department Head of Computer Science. He now prefers to be called by this name. According to Hall, his nickname "came from a time when I had less control over my temper."

He has worked for Western Electric Corporation, Aetna Life and Casualty, Bell Laboratories, Digital Equipment Corporation, VA Linux Systems, and SGI. He is currently the CTO and ambassador of Koolu.

It was during his time with Digital that he initially became interested in Linux, and was instrumental in obtaining equipment and resources for Linus Torvalds to accomplish his first port, to Digital's Alpha platform. It was also in this general timeframe that Hall, who lives in New Hampshire, started the Greater New Hampshire Linux Users' Group. Hall has UNIX as his New Hampshire vanity license plate.

Hall serves on the boards of several companies, and several non-profit organizations, including the USENIX Association. He is a well known elder statesman of the programming community, and a respected figure in the free software movement. At the UK Linux and Open Source Awards 2006, Hall was honoured with a Lifetime Recognition Award for his services to the open source community.
Hall holds a Master of Science in Computer Science from Rensselaer Polytechnic Institute (1977) and a Bachelor of Science in Commerce and Engineering from Drexel University (1973).