Quoting the engineering team from Boston Dynamics:

It is a quadruped robot that walks, runs, and climbs on rough terrain and carries heavy loads. BigDog is powered by a gasoline engine that drives a hydraulic actuation system. BigDog’s legs are articulated like an animal’s, and have compliant elements that absorb shock and recycle energy from one step to the next. BigDog is the size of a large dog or small mule.

Second thought: US Army wants one of those. Right, the United States Department of Defense resp. the Defense Advanced Research Projects Agency is founder of the BigDog Research Program; while Boston Dynamics is the engineering company that specializes in robotics and human simulation.
They began as a spinoff of the Massachusetts Institute of Technology where Marc Raibert and his colleagues first developed robots that run and maneuver like animals.

Question: Who holds the intellectual property? Engineers or military? I simply hope that civil usage of these walking robots will be first.