I'm still trying to figure out what imdbapi is doing exactly. They cite freebase and wikipedia (at the bottom of their home page) but neither of those have imdb ratings.

What data imdb makes available is here, along with references to their ToS: http://www.imdb.com/interfaces/

It seems the data IMDB makes available is nearly useless (or I'm misunderstanding it) and doesn't include ratings.

This implies IMDB API is scraping IMDB. Whether that's legal or not, I can't say. But I can say this- IMDB was created on the work of many users who licensed their efforts under terms that were, in my opinion, broken when IMDB sold to Amazon, and thus I think scraping is moral.