Minor nit: I agree 110% with the article's point about the need to "Prominently feature a '[noun] is' paragraph", but the example they give isn't that great:

"An excellent example of this in action is on libcinder.org where it states right up front: 'Cinder is a community-developed, free and open source library for professional-quality creative coding in C++.' Perfect!"

I'd push back on the assertion that this is perfect. "Library for professional-quality creative coding in C++" is actually a pretty fuzzy, non-descriptive way to describe your project. The only real thing you've learned after reading it is that it's for C++; you don't know anything specific about what it does, just that it's "professional" and "creative."

The Cinder developers actually have a much better one-sentence description at the top of their About page (http://libcinder.org/about/):

"Cinder provides a powerful, intuitive toolbox for programming graphics, audio, video, networking, image processing and computational geometry."

There's still some fluffy words in there ("powerful," "intuitive"), but overall it gives you a much better answer to the question "What is this?" than the tagline cited in the article does.