There is no set hard and fast rules so this is simply my opinion.
Google is pretty lenient if the percentage of content you have copied is low compared to the rest of your page.
Duplication issues can also be overcome if you have other good SEO trust signals i.e. good back links, established domain, unique content etc. I assume this is why Rotten Tomatoes get away with duplication issues as they have an established brand.
As long as you are citing the original source and the duplicated content is not a large percentage of your page then you should be ok.