What are the difference/similarities between React (app framework from Facebook) and react.js (reactive extensions for JS)?

What are the difference/similarities between React (app framework from
Facebook) and react.js (reactive extensions for JS)?

I recently learned about Facebook/Instagram's app framework for JavaScript
called "React" and wanted to look more into it. However, I found myself
getting conflicting search results, as there is another library of a
similar name. So, my question is this: Are there similarities between the
two, or could someone do a better job at naming?
React
http://facebook.github.io/react/index.html
react.js
http://www.reactjs.com/