Look at the healthcare.gov source and you see the following technologies in use:

  - jQuery 1.8.2
  - Backbone 0.9.2
  - Bootstrap 2.3.2

You may need to look inside the all.css and all.js files.

Page Speed: 92/100 YSlow!: C, 76/100

At least on the homepage I don't see Backbone actually being used.