I split the SASS file, so the developer can decide which fonts and styles she or he really needs.
Installable via Bower:
bower install open-sans-fontface
Our repository: http://fontfacekit.github.com/open-sans
Google Web Fonts: http://www.google.com/fonts/specimen/Open+Sans
Contact @gustavohenke if you want to maintain your own font-face in this repository.