The Free On-line Dictionary of Computing (18 March 2015):
A project suggested by J C R Licklider; its founding
director was MIT Prof. Robert M Fano. MAC stood for
Multiple Access Computers on the 5th floor of Tech Square, and
Man and Computer on the 9th floor. The major efforts were
Corbato's Multics development and Marvin Minsky's
Artificial Intelligence Laboratory. In 1963 Project MAC
hosted a summer study, which brought many well-known computer
scientists to Cambridge to use CTSS and to discuss the
future of computing.
Funding for Project MAC was provided by the Information
Processing Techniques Office of the Advanced Research
Projects Agency (ARPA) of the US Department of Defense.
See also Early PL/I, MacLisp, MACSYMA, MDL,