If I recall correctly, a summer intern in the AI section under the Mission Planning Directorate, whose name I have forgotten, developed a prototype or a proof-of-concept of CLIPS. At the time, 1984-ish, the AI group at JSC had many expensive Symbolics and Lisp Machine computers running ART. The intern's project showed that a pattern matching rules based engine could be developed in a conventional programing language for distribution to traditional cost effective hardware.
In 1984, C was considered a new programming language. The VAX first came out in 1977, and the Sun 1 in 1982. Traditional hardware in 1984 would be an IBM mainframe.