Is there a copy of their interpreter available? I'd like to see how the relations are setup to be able to "run backwards".

They said they would send it along, but they wanted to make the parser relational as well. When I get it I'll do a write up about it.

I believe the official Kanren/miniKanren source is at http://kanren.sourceforge.net and the cKanren source is at https://github.com/calvis/cKanren

I think he was asking about the interpreter they demoed during their talk. A more up-to-date version of miniKanren as well as many interesting variants can be found here: http://code.google.com/p/iucs-relational-research/

For small crud apps you can avoid the java baggage.

Using ring and ring-servlet you can build the servlet app engine wants. Libraries like compojure build on top of ring.

The datastore can be accessed using http://github.com/r0man/appengine-clj or http://github.com/smartrevolution/clj-gae-datastore.

Accessing the blobstore has not been abstracted away yet and requires a bit of work to get uploads acting correctly with ring/compojure.

I've not touched task queues, xmpp, mail, or memcache and have not seen any abstractions for them.