After three years of service the server has been taken down.
TLDR: there is no alternative. As a stopgap start using Google alternatives like DuckDuckGo or Startpage and Firefox's new Tracking Protection.
No more effort will be put into hosting this service. The add-on does not work with Firefox 32 and later, the SSL certificate expired and support for Ubuntu 10.04 ends in April 2015. There are no plans to build a similar add-on, nor is there anyone in the community working on this as far as I know of.
Moreover an attempt (dutch) to see if there is anyone who wants to cooperate in writing and supporting a new server using node.js didn't get any response. If you want to discuss this please mail me.
Given the lack of any similar alternatives I would suggest to switch to DuckDuckGo or Startpage and start using Firefox's new Tracking Protection that Mozilla is building.
Because the add-on no longer works since Firefox 32 (released on September 2) and the SSL certificate expires soon the service will be taken down on November 1, 2014.
Both the server and the add-on suffer from serious bitrot. Since Firefox 32 is released it is known that some users can not connect anymore.
Rewriting the original authors add-on and server in node.js is somewhere on the back of my mind but I don't see it happen anytime soon, because of a lack of time. If you are interested in leading or helping with this effort please let me know.