> Two new specific software languages known as "PROL-2" (used by the on-board computers) and "DIPOL" (used by ground computers using vehicle testing) [...] were developed for Buran
So I guess the what the CIA report refers to as Prolog is PROL-2. But is this really a Prolog variant? That seems like an unlikely choice of language for a real-time system.
Later, both of these languages developed into DRAKON , and looking at the Wikipedia page that language doesn't appear very Prolog-like, at least not superficially.
On the other hand, here is a reddit comment that claims that is was indeed a Prolog variant, but it doesn't cite the source.
My old German university's web server was written in prolog, so it's not completeley inconceivable for a spacecraft, but I'd like to see more evidence.