[cenamus]

PS was actually used for OS graphics multiple times (with more adaptions of course)

https://en.m.wikipedia.org/wiki/Display_PostScript

[hamburglar]

Yes but using raw postscript in this perverse way to get interactivity is truly inspired. My hat is off to the author.

[pjmlp]

Not really, that is exactly how it was used in Sun NeWS.

https://en.m.wikipedia.org/wiki/NeWS

You would write full blown GUI apps in Postscript with some C glue.