MOPAC does not have a specific graphical user interface. The program can be used on its own, or with an in-house G.U.I, or with a commercial G.U.I. The reason for the lack of a specific G.U.I. is simple: my objective is to produce a semiempirical computational chemistry 'engine'. This engine can then be joined, possibly with modifications, to different graphics packages. In order to facilitate this, the input and output of MOPAC has been kept as constant as possible.
There is a list of readily available and supported G.U.I.s.