Drupal is an open source content management system--which means that thousands of programmers, including the dudes who built Shareable.net, have collaborated in creating and managing it.
As John Scott of Open Source for America told tech maven Tim O'Reilly: "This is great news not only for the use of open source software, but the validation of the open source development model. The White House's adoption of community-based software provides a great example for the rest of the government to follow." O'Reilly notes:
Drupal has a huge library of user-contributed modules that will provide functionality the White House can use to expand its social media capabilities, with everything from super-scalable live chats to multi-lingual support. In many ways, this is the complement to the Government as Platform mantra I've been chanting in Washington. When you build a vibrant, extensible platform, others add value to the foundation you establish; when you join such a platform, you get the benefit of all those features you didn't have to develop yourself.