The U.S. government has long used open-source software. Beowulf, the popular Linux-based clustering and super-computer program, for example, got its start at NASA's Goddard Space Flight Center. Under President Obama, open-source software though is showing up in more and more places.
That shouldn't be too surprising. You can argue that one major reason why Obama became president was because of his team's skill in combing old-fashioned grassroots politics with 21st-century social networking. Obama, although a lawyer by training, is easily the most technical of our presidents since Hoover, an engineer, held office in the late 1920s and early 30s.
With a tech-savvy president in the Oval Office, it makes perfect sense for Obama and his team to be adopting open-source software. For example, Obama and his team started using Drupal (a popular open-source CMS [content management system]) and Linux to run Web sites back in February. The first Federal site to make the jump to Drupal was Recovery.com, which tracks Recovery Act spending.
You probably only noticed that transition if you were a Drupal user. Now, though, Obama and his staff have switched the White House's own Web site to Linux and Drupal. The executive branch's programmers made the change to the White House site not because they wanted to change its look; according to an AP report and my poking around the site, the White House site looks the same as ever. The reason why they made the change was the reason why many people switch to Linux and open-source programs: it's more secure.