For those interested in code analysis and dev tools, another library you might want to check out is srclib (I'm one of the authors). srclib is an open-source polyglot code analysis library designed for editors and code explorers. Its mission, supporting a common language-independent schema to support building better language-aware tools, is closely aligned with Kythe's. There's documentation and a succinct description of the problem we're trying to solve at https://srclib.org.
srclib currently supports Go, Java, Python, JavaScript, Ruby, Haskell, and soon PHP. There's a simple command line API that editor plugins can call, and currently there are srclib plugins for Emacs, Sublime, and Atom. srclib also powers https://sourcegraph.com.
I'm looking forward to seeing where Kythe goes and hopefully integrating Kythe and srclib. I think this is a huge step forward toward better tools for programmers. Just ask anyone who works/used to work at Google about the quality of their internal dev tools vs. the outside world. Thanks to the Kythe team for sharing this with the world!