Consider Emacs vs. Notepad++, for the purpose of editing code. Emacs in this example represents "maximal flexibility" for having a configuration interface where almost every aspect of its function can be (re)programmed, and Notepad++ represents "maximal cooperation" for having a configuration interface and limited toolset tailored to the task specifically at hand (editing code). I'm not going to contribute code to either project; submitting patches for a "maximally cooperative" system to adapt it to your use case is just an advanced and inconvenient form of "maximal flexibility".
In my experience this has the opposite relationship to that described in the article. Getting started with Emacs is a significant investment (as per the article, "everything is possible but nothing is easy"), while Notepad++ is pretty much pick-up-and-go out of the box, but over time the extensibility of the former pays off in a better functionality/amount of work ratio.
There is an example of "maximal flexibility" in the article, but none for "maximal cooperation", and I'd like to see one.