That somebody is German engineering firm Festo. The company, which has a history of turning to nature for inspiration, is also responsible for this mechanical seagull and these claw-tipped Doc Ock arms (which were modeled after an elephant's trunk).
IEEE Spectrum has the details on the roo-bot's technical specs, which actually sound pretty cool:
BionicKangaroo is able to realistically emulate the jumping behavior of real kangaroos, which means that it can efficiently recover energy from one jump to help it make another jump. Without this capability, kangaroos (real ones) would get very very tired very very quickly, but by using their tendons like elastic springs, the animals can bound at high speeds efficiently for substantial periods of time.
BionicKangaroo emulates this with an actual elastic spring, which partially "charges" the legs on landing. The entire robotic animal weighs just 7 kilograms and stands a meter high, but it can jump 0.4 meter vertically and 0.8 meters horizontally, which is fairly impressive.
Of course, an internal power source is necessary as well, and BionicKangaroo relies on either a small compressor or a storage tank to provide high pressure air for the pneumatic muscles that power the jumping. Lightweight batteries drive everything, and a sophisticated kinematic control system keep the robot from toppling over. Control, as you might have noticed in the video, is gesture-based, via a Thalmic Labs Myo armband.