One of the authors here. The neat thing about this set up is that these streaming examples are executing against a real stream processor in the browser.
The interactive examples were built using [Onyx](https://github.com/onyx-platform/onyx) and it's cross-compiled JavaScript sibling, [onyx-local-rt](https://github.com/onyx-platform/onyx-local-rt).
Distributed Masonry uses Clojure to build Onyx [1], an open source distributed batch and streaming platform. We also build a realtime application platform named Pyroclast [2] directly on top of Onyx. Our code base is written entirely in Clojure. The architecture we've ended up with is hands down the cleanest I've ever worked on.