SOPA specifically (without actually naming it) calls out addons.mozilla.org for the whole mafiaafire thing -- so under SOPA, this add-on wouldn't be allowed to stay up. "[T]his version targets software developers and distributors as well. It allows the Attorney General (doing Hollywood or trademark holders' bidding) to go after more or less anyone who provides or offers a product or service that could be used to get…
https://addons.mozilla.org/en-US/firefox/addon/desopa/
or
[add-ons mozilla base URL ] (slash) en-US (slash) firefox (slash) addon (slash) desopa (slash optional)
in case it is filtered.
Disclaimer: I developed it