WordPress multisite with same content

This would take a little bit of work, but you could adapt code from this plugin:

http://www.mihaivalentin.com/different-wordpress-theme-depending-of-the-current-user/

First you would point all the domains to the same site.

This plugin changes the current theme depending on the user logged in. But you could change the logic to change the theme depending on the referrer address.

if($_SERVER['HTTP_HOST'] == 'site1.com' ):
//one theme
elseif( $_SERVER['HTTP_HOST'] == 'site2.com'):
//another theme
endif;