Just a quick update to let you all know a Firefox extension for unsourced.org is under development.
For the technically-minded:
The source code is at https://github.com/bcampbell/unsourced-firefox
It uses the Firefox Add-on SDK, so if you have that installed you can simply clone the github repository above and use "cfx run" to try it out.
The plan is to quickly get the firefox extension on par with the Chrome one. They can share a lot of the core code, so future improvements should improve both versions.