5 つ星中 4つの評価を受けています

I'm not sure why Mozilla themselves didn't write a better description, but here is what I got from the project's official page:

"In short, Jetpack is an API for allowing you to write Firefox add-ons using the web technologies you already know."

Source: https://jetpack.mozillalabs.com/

これは以前のバージョン (0.2.1) についてのレビューです。