|User since||Sept. 9, 2008|
|Number of add-ons developed||0 add-ons|
|Average rating of developer's add-ons||Not yet rated|
Rated 4 out of 5 stars
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."