After you learn to write miniKanren programs, you'll want to know how it works. The original miniKanren implementation combines the core of the logic processing with some crazy Scheme macrology for building a nice syntax. I spent several days puzzling through the back page of "The Reasoned Schemer" without really getting it.
Luckily, you can now read the microKanren paper (http://webyrd.net/scheme-2013/papers/HemannMuKanren2013.pdf) which breaks apart the "core" portion of the logic processing into a purely-functional bit, separate from the macros for the nice syntax.
That little core can be implemented very easily in almost any language with closures. For some fun, I implemented it in JavaScript using some sweet.js macros on top. It took about an hour to get something working, and a day or two to fix more bugs, and now I understand how kanren works. Plus I added some tracing in so I can see how different steps in the program cause the logic variables to get bound: http://adamsolove.com/microScopeKanren/
Definitely worth the time if you're interested in relational programming.
This kind of languages is extremely useful, since many problems maps nicely to a logical or relational model.
I'm using a PAIP-style embedded Prolog and an optimised Datalog for fast prototyping compiler passes - things like alias analysis, implementing type systems (e.g., Hindley-Milner maps to Prolog naturally), constant folding, DCE, Array-SSA, and many more.
Harlan is using cKanren for region inference and some other passes.
Minikanren is featured in a follow up to 'Seven Programming Languages in 7 Weeks' by Manning Pubs. 'Seven More Programming Languages in Seven Weeks'. I think Elixir and Julia are also going to be included in the book. Anyway, if anyone here is into Manning books there's a MiniKanren chapter to look forward to. Disclaimer?!: I do not work for Manning. Just a reader.
There was a nice interview with Will Byrd a couple episodes ago on the Cognicast (Cognitect's Podcast). He discussed MiniKanren along with a ton of other work and thoughts. Recommended listening.
So... Kanren doesn't look like it's actively developed anymore and now folks are working on MiniKanren. The guys doing MiniKanren appear to always work in Scheme, although lots of other folks re-implement the work they publish in whatever language they're currently infatuated with.
Clojure's Core-Logic is one such project and it appears to have the most active community... but it's not really accurate to call it a faithful implementation of either Kanren or MiniKanren; rather they've used those projects as a starting point and by now they've added various other capabilities or avoided/removed others.
And now there's microKanren, an even more simplified implementation that is "entirely functional and devoid of macros ... [making it] more directly portable than that of other miniKanren languages."
Luckily, you can now read the microKanren paper (http://webyrd.net/scheme-2013/papers/HemannMuKanren2013.pdf) which breaks apart the "core" portion of the logic processing into a purely-functional bit, separate from the macros for the nice syntax.
That little core can be implemented very easily in almost any language with closures. For some fun, I implemented it in JavaScript using some sweet.js macros on top. It took about an hour to get something working, and a day or two to fix more bugs, and now I understand how kanren works. Plus I added some tracing in so I can see how different steps in the program cause the logic variables to get bound: http://adamsolove.com/microScopeKanren/
Definitely worth the time if you're interested in relational programming.