I have lots of languages coexisting from EDL to Java to C++ to C to Python.  I integrate with message passing / RPC, so there is no issue with binary compatibility.  Struct/copycd/class versions of data layout are easily translated automatically.  My brother uses JSON source for data definitions, and translates that to headers/copycd/etc for various languages.

A lot of people use JSON for messages.  I respect that and have no problem interacting with that, but it is slower.