The Flowers Lab, a french research team, is behind Poppy a humanoid which is 3D printed (see Video 1). They are have released both the hardware and the software under an open source license.
Robotis-OP (Formerly Darwin-OP)
Poppy is competing with yet another open source humanoid robots: the Darwin-OP from Robotis (see Video 2). Indeed the OP stands for Open Plateform. Files describing both Darwin-OP’s hardware (mechanics and electronics) and software are freely available from source forge.
Build Your Own Cheap Humanoid Robot
One of the reason Robotis-OP and Poppy are so expensive is related to the number and the power of servomotors they rely on. Those robots have many joints, which means as many servos. Beside, the scale of the robots implies the use of servos capable of delivering enough torque. Those are typically the Dynamixel MX servos that can cost up to $500 each!
There exist cheap and yet good enough servo motors that can be used for making simple humanoid robots. So, you can make your tiny humanoid for few hundred bucks. For example the Dynamixel AX12 cost about $40 each. They are also very easy to program, and share many interesting features with the MX series. This includes synchronized movements that allow controlling many servos at once. Ideal for programming bipedal walk or different gaits for legged robots.