Right now the project is developing one product: the Add-on SDK.
The Add-on Builder in is now in read-only mode and will be turned off completely in April 2014. Please download your data before then. Learn [https://blog.mozilla.org/addons/2013/12/18/add-on-builder/ more].
* The Add-on SDK is a locally-hosted development environment that allows you to easily build add-ons for Firefox.