I believe Jerry had an advertising deal with Yamaha back in the mid-to-late '80s and that's probably the reason he gave the company
an actual screen credit on Runaway.
The Yamaha keys included the GS-1 and a rack of three DX-7s. The other gear/synths used on this score were a Roland MKB-1000 MIDI keyboard controller, Roland MSQ-700 sequencer, Rhodes Chroma, Minimoog, Jupiter-8, Memorymoog, Oberheim system (OB-8, DMX & DSX), Prophet T8, acoustic grand piano, a rented Emulator (percussion sounds/effects) and a Doctor Click (mainly used for the drum machines and to run the arpeggiators in the various synths).
Jerry wrote out the music as if it were an orchestral score* and did most of the programming and playing.
* but the orchestration was not done in imitation of an orchestra.
EDIT: the same setup as above, minus the Emulator, was used for both Supergirl and Gremlins. And for 1985's Legend he used
a Yamaha DX-7, Roland Jupiter 8, Memorymoog, Oberheim OB-8, DMX & DSX, and Sequential Prophet T8 along with a large orchestra and choir.
"The (Yamaha) CS-80 is a step ahead in keyboard control, and a generation behind in digital control" -- Dan Wyman, Jan 1979