[seanmcdirmid]

APL is far from dead, there is a lot of living legacy code and old timers with APL skills still actively using it commercially.

Prolog on the other hand...I'm not aware of any commercial projects actively using it, but it is still alive as a hobbyist/learning language.

[Solarsail]

Well, if you're only looking for logic languages instead of Prolog itself, then there's http://www.princexml.com/ written in Mercury.

[seanmcdirmid]

Of course. Datalog also gets alot of use in industry.