On the wikipedia page for the game [1], it says that it uses Pinball 2000 hardware. And on the wikipedia page for Pinball 2000 [2], it uses Xina (Xina is not Apple) and not Xinu. Is there another variant of the OS?
[1] https://en.wikipedia.org/wiki/Star_Wars_Episode_I_(pinball)
The "Pinball 2000 hardware" setup was an ATX motherboard running a MediaGX CPU (x86 clone, it lives on as AMD Geode). It also had a custom PCI card for storage and sound DSP, and a secondary board connected by parallel port for driving lamps and solenoids.
XINA was an application layer on top of XINU that handled the executive tasks of running a pinball machine, and also abstracted the various hardware features. We used Allegro as the graphics SDK.
The name XINA was inspired by XINU, and was an acronym for "XINA Is Not APPLE". APPLE was the previous pinball programming system, no connection to the computer company.
SG isn't making pinball machines but apparently has licensed the code to an outside group to maybe remake old games or whatever.