My gut feeling is that the 'frameworks are for prototypes, libraries are for production' camp is closest to the money, but (a) I have no actual data and (b) different approaches to frameworks will have different outcomes.
Under that definition, ReactJS is strictly a framework. But we tend to look at it as a library since unlike other monolithic frameworks (Angular, Rails etc.), it is quite small, composes well, and is not overly prescriptive.
While I don't think FOAM is the next-big-thing in Javascript frameworks (that award goes to React's component model), I am happy to see it focusing on the primacy of the data-structure and recognizing that good code flows from a good data structure. We can already use that philosophy in React by ensuring all components are annotated with propTypes, using a statically typed language (TypeScript), and clearly defining the API schema using something like JSON Schema (http://spacetelescope.github.io/understanding-json-schema/ab...).
> a mature app written this way
I've added links a number links to FOAM apps for you at the bottom of http://foamdev.com.
We have a number of mature apps. QuickBug, which is a codesite issue tracker, is about two years old. MBug is a mobile version, is about a year old. The ChromeOS calculator was written last summer as a demo but went into production just recently. There's also a rough but working GMail client. The Chrome App Builder is also in production, but, unlike the other apps, isn't open-sourced. We also have a couple very large internal Google apps that I can't talk about.
> project timeline FOAM was started in 2011, and generated its first production code, in C++ and JS for Chrome, in early 2012.
> war stories
Here's one: https://docs.google.com/presentation/d/139TUw8tLtqRzFSHGoLTQ...
I have several others as well, but I would need to scrub them before making them public.
https://docs.google.com/presentation/d/1Ipt0hu2PHDgL8HCxkZN2...
The first part of the slides is on using the apps and the second part has a bit about how we developed it (but without speaker notes, it may not make a lot of sense).