Currently, Agility Robotics is selling Cassie , a two-legged robot with no arms, to researchers for robotics work. (Cassie is named after the cassowary, a two-legged flightless bird from Australia and New Zealand.)

That's according to Damion Shelton, the CEO and co-founder of Agility Robotics , a start-up based in Albany, Oregon, which is building robots that can walk and run.

A world where humanoid robots deliver your packages to your door may be as little as two to three years away.

So far, Agility Robotics has sold three Cassie robots (University of Michigan is a customer, for example) and has sales for another three in progress. The goal is to sell another six Cassie robots, "so optimistically 12 customers total for the entire production run of Cassie," Shelton tells CNBC Make It. Each Cassie costs less than $300,000.

Robot testing in the rain. Just another day on North Campus.

"That is obviously, though, a relatively compact market, and is not why we're doing the company," says Shelton, in an interview with CNBC Make It.

Indeed, the next generation of the company's legged robots will also have arms, says Shelton. And one target use for the more humanoid robot will be carrying packages from delivery trucks to your door.

Shelton says his house is a perfect example of how a legged robot would assist in delivery. He has a steep driveway, so delivery trucks often park at the bottom and the driver has to walk the package up to his doorstep.

"We see a lot of that kind of general class of problem ... which is that the last-mile solution works for most of the last mile and then not the last 50 to 100 feet," Shelton tells CNBC Make It.

"Because those [last yards] tend to be environments that are designed for people, and people have legs. So things that are very easy for a person to navigate — like a curb or a flight of steps or toys left in the front yard or whatever — things that are very easy for people to kind of move through without thinking about it" are roadblocks for anything with wheels, he says.

Even further in the future, Agility Robotics envisions using the robots in conjunction with autonomous vehicles.

Agility Robotics hopes to be testing humanoid robots delivering packages in pilot studies by the end of 2018. Commercial deployment will start on a limited basis in two to three years, says Shelton. The deliveries will start in areas of the country with mild environments, like Southern California. By 2021 or 2022 Agility Robotics expects to see slightly more widespread use of its products for last-mile package delivery, says Shelton. Agility Robotics could either sell or lease the robots to delivery companies.

For a roboticist, a future where legged robots deliver packages to your door may be exciting, but for regular people, the idea of humanoid robots can be frightening.

Robots standing around: fun. What's more fun? An office tour. With robots.

"We've made deliberate choices to use softer shapes, bright colors, not going for super anthropomorphic," says Shelton. "There is a need to make sure that you know the robots don't come across as threatening and that we are mindful of people's reactions to them.

"I would say that that is something that the robotics community as a whole has tended to not think through," says Shelton. "[P]eople have tended to produce things that look cool to robot enthusiasts, which end up with sort of a science fiction-y kind of look to them — a lot of white colors or shiny metal that looks a lot more 'Terminatory' than something you would want to have running around your house."