DTSS
The first commercial time-sharing system, created by Dartmouth College and sold by General Electric around 1967.
GE's Information Service Divsion (ISD) marketed DTSS which was running on a system called GE-265 (a combination of the front-end processor the Datanet-30 and the GE-235).
DTSS was ported (and significantly improved by GE ISD around 1965-1966 on a combination of DN-30 and GE-635). This proprietary system, called Mk-II, later improved by GE and renamed Mk-III, is still working today (1997) as part of the GE service bureau that also includes IBM and Unix computers.