GNU Prolog is a free implementation (under GPL) of the logic programming language PROLOG. It can compile to native machine code which is extremely fast in execution. Another feature is the included constraint solver.
Fi-shell is a front-end to your system shell. It provides nonblocking i/o (concurrency) and pattern maching that is both easy to remember and readable (logic programming)
A group of systems for building network-oriented intelligent agents, consisting an agent communications infrastructure, April - an agent construction programming language, Go! - a logic programming language and DialoX - an XML-based user interface engine
Mercury is a modern logic/functional programming language. The Mercury system includes a
compiler, debugger, libraries, sample code, profilers, etc. Mercury is designed to be the successor
of logic programming languages such as Prolog.