Download
JJPS is free to use and download
Version 0.2.1; for Firefox 3+
Installation instructions
You will have to specifically "allow" this site to install the JJPS extension. When you click on the "Download Now!" button, a small window will appear in which you will have to click "allow". When the next window pops up, you will be able to click "Install now" after a few seconds wait. Do so, wait for the extension to download and install, and then restart your browser.
Extension Source Code
The extension for the source code can be found within the extension itself; simply unzip the .xpi file to look inside. The most up-to-date, and not necessarily functional, code can be found in the git repository on github.