Yelp is a multi MLOC Python code base. AFAIK YouTube is slowly being ported from Python to Go.

There are plenty of other large codebases in dynamic languages:

  - Wikipedia and Facebook written in PHP
  - Twitter was originally written in RoR

To be honest, it's my personal opinion that good static languages (i.e. type inferenced) are better than dynamic languages. I believe it's situational compared to traditional static languages (e.g. Java, C++).