Boston Dynamics has won contracts worth US$140 million ($169 million) since 2000 from the DoD and its agencies. The company boasts that it advises and assists the "US Army, Navy and Marine Corps" on developing "the most advanced robots on earth". By comparison, Google's income from defence work over the same period was US$300,000.
Experts and campaigners yesterday voiced concern that despite Google's insistence that it does not intend to become a defence contractor, the acquisition of a company with established links to the military might make such work hard to resist.
With inventions such as Big Dog, primarily designed to carry loads over rough terrain and with the uncanny ability to recover from a human kick, Boston Dynamics could move into the sphere of transporting weaponry rather than producing it.
Professor Noel Sharkey, a leading artificial intelligence and robotics expert, based at the University of Sheffield, said: "I would like to think that Google will actually use the advanced technology to build an astonishing civil robot - maybe one that can deliver parcels or help in the home. But the multimillion-dollar lure of military contracts may push them into the dark side. Let us hope not."
The Boston Dynamics deal, for an undisclosed sum, brought inevitable - if overblown - comparisons between Google and Skynet, the rogue computer system which manages to wipe out much of humanity in the Terminator film series.
The robotics company has blazed a trail in producing some extraordinary machines capable of operating in harsh environments, including the Cheetah, which can run at 46km/h - faster than Usain Bolt, and Atlas, a humanoid robot built under a US$10.8 million deal with the Pentagon's Defence Advanced Research Projects Agency.
But rather than hunting down hapless homo sapiens for some sort of robotic genocide, the maker of Atlas and its stablemates insists they are designed to help humanity out of self-inflicted disasters.
Dr Marc Raibert, a former professor at the Massachusetts Institute of Technology who founded Boston Dynamics, has insisted his company does not exist to be a military contractor and is motivated by advancing robotics.
For his part, Rubin has described his project as a "moonshot" - the term Google applies to its slightly more outlandish schemes, such as self-driving cars and using a network of blimps to bounce internet signals to remote regions.
But while a world of autonomous cars remains some way off, it is likely Google is expecting a quicker return on its robotic investments.
Amazon has already spent nearly 500 million ($984 million) on automating its warehouses and announced earlier this month - amid a lot of scepticism - that it is developing delivery drones designed to drop a package on doorsteps for use within the next five years.
The question is whether Google can finesse Big Dog and its brethren sufficiently to assist an old person out shopping or run to a stricken hiker's aid, rather than launching bits of masonry like a siege engine.
- Independent