Although the article begins with a photo of a quadruped robot, it focuses mostly on the software - path planning side of robotics. While still a very active research field, BD and any other places doing legs are much more concerned with mechanical - dynamics, actuators, battery, locomotion problems.

If you want to do some real work on those, pursuing grad school in Electrical (actuators, battery) / Mechanical Engineering (legs, locomotion) is the best, and for the legged robots industry probably the only way (same goes for biomimetics - robot hands). The related research area encapsulating the above is called passive dynamics and primarily is a control theory-based field.