Is there any library, preferably in python but at least open source, that can summarize and or simplify natural-language text?
I'm not sure if there is currently any libraries that do this, as text summarization, or at least understandable text summarization isn't something that will be easily accomplished by a simple plug & play library.
Here are a few links that I managed to find regarding projects / resources that are related to text summarization to get you started:
Hope that helps :)