What's driving the adoption of WordPress, Drupal, and many other open source applications is a need to "do more with less," adopt modern technologies and development practices, and avoid more costly failures. The UK's executive director of digital, Mike Bracken, told me in February 2014 that this approach to building digital services is "vastly cheaper," a claim that 18F will be proving out in the years to come.
"Healthcare.gov was a watershed moment in the conversion," said Balter. "An inflection point. Geeks in government had been saying for a long time that traditional, heavyweight large dollar, long-term enterprise projects were far less resilient than more modern, open systems. The traditional management playbook has always been to throw more money and bodies at the problem. Healthcare.gov (among other examples) show that that's not the answer. No software is perfect, but today agencies realize that communicating more, not less, working openly, with shared tools, and shipping 0.1."
It's no accident that open source projects are driving innovation in multiple sectors and parts of government. The defense community has been a notable adopter of open source in many contexts, most recently in its battleships. Open source software and hardware will be core to adaptable platforms deployed to battlefields around the world. "If you can't hack it, don't pack it" is a mantra I've heard from more than one military veteran over the years, and one that's been heard at DARPA more than once.