Yep, Kythe is the open-source version of grok. It's awesome, and the srclib team is in touch with the Kythe team at Google to build on top of their analysis libs (for C++ and Java).

Long term vision is to get rid of the "my editor X doesn't support language Y" problem as well as build a lot of other multi-language analysis tools on top of it. Shameless plug: if you care about developer productivity, join us!