I worked with Atlas during 2013 at WPI. Siyuan Feng just defended his thesis on Online Hierarchical Optimization for Humanoid Control for controlling Atlas during the DRC. The controller used is not as well refined as BD's controller, but I believe it stands in the same principles, and relies on ZMP.

[1] https://www.youtube.com/watch?v=QcBYhR0DbbU [2] http://www.cs.cmu.edu/~sfeng/sf_thesis.pdf