Don't just go and add foreign repositories to your system. There is a reason
why all distributions use their own repository. It will only create problems
later on if you do so. The "I have to reinstall the whole system to fix it"
kind of problems. Not necessarily, but possible.
You can download the binary package built for 32-bit or 64-bit GNU/Linux
(Magic Banana's second link is the 64-bit version).
Once you download that, extract the archive in your home directory. Then you
can already start the application from there. You can also edit the
application menu and add a starter for IceCat, or add a starter somewhere
else, like desktop etc.
It does leave you without updates for the browser though.
If you want to have updates, you can use this: BrunoAlexandreMiguel GNU
IceCat PPA.
Follow the instructions there, and you'll be able to have an apt-managed
installation of IceCat.
