Actually, this type of languages has a much different (and simpler) semantics than Prolog, which means that one doesn’t require to be a Prolog afficionado. The main similarities are the syntax, logic variables and the concept of (output) unification. As doublec has pointed out, there is an article by me that tries to give an introduction into the topic. The Strand book is highly recommended, very accessible and explains the basic concepts in a step-by-step manner.

FLENG/FGHC/Strand (and other languages of this family) are highly parallel, which has interesting implications: concurrency is always there and you concentrate on what to make sequential (there are several strategies and tools for this). Stream processing is a very powerful abstraction mechanism, and logic variables with the possibility of data structures having “holes” allows straightforward parallelisation of tasks. I would think this is very handy for GUIs, games and all sorts of simulations.

It’s a different way of programming, but it really opened my mind to dive deeper into these concepts. This implementation is an attempt to be simple, yet practical. The language makes multi-threaded programming much easier, compared to traditional techniques, which are, IMHO, lacking in elegance and convenience.

Have you seen their The Joy of Concurrent Logic Programming article? The Strand book is also a great read.