Addamax was an American software company that developed Trusted operating systems based on UNIX System V and Berkeley Software Distribution (BSD) variants of UNIX. The company was founded in 1986 in Champaign, Illinois by Peter A. Alsberg and had a sales and development office in Gaithersburg, Maryland. Addamax filed a high-profile antitrust lawsuit in 1991 against the Open Software Foundation (OSF), alleging that OSF created a cartel that controlled the UNIX operating system and exerted monopsony price fixing and led to the company going out of business.