You can download it from: http://www.metaproducts.com/download/betas/mpint.xpi
To install the plugin, please drag and drop the file to FireFox window using Windows Explorer. Then please restart FireFox application.
Now you can use the link right-click menu item "Download Express: download this file." Also, FireFox will offer you to use Download Express to download files.
The K-meleon browser is very customizable because of it`s macro language support.
Using this macro language I created a macro which allows the use of Download Express with the K-Meleon browser.
The macro can be found here:
Thank you very much for your kmeleon plugin!