https://www.mediawiki.org/wiki/Extension:Blackout
This is NOT the code that the Wikimedia Foundation is using for the
SOPA/PIPA blackout. (We'll be putting up a technical guide sometime in
the next 6 hours explaining how we're implementing this, mentioning that
you can't edit via the API, etc.) This is an extension developed by
Gregory Varnum and John Du Hart to help other MediaWiki sites black out.
The code's at:
http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/Blackout/
That page also links to other resources and methods for anti-SOPA
JavaScript and so on.
--
Sumana Harihareswara
Volunteer Development Coordinator
Wikimedia Foundation