A big point of using Prolog for the commercial projects fitting its niche (1) is that it's based on an ISO standard, though, and implementations are (theoretically) interchangeable. To make Prolog programs actually portable across major Prolog implementations, there's been the Prolog Commons initiative for an extended standard predicate lib.
1) personally I think Prolog is much more broadly applicable in all kinds of apps rather than just type inference, policy languages, games; but with the recent rise of Datalog as actual query and inference language (and not just in academic database literature), it seems Prolog's time has finally come
1) personally I think Prolog is much more broadly applicable in all kinds of apps rather than just type inference, policy languages, games; but with the recent rise of Datalog as actual query and inference language (and not just in academic database literature), it seems Prolog's time has finally come
[2]: http://www.prolog-commons.org/