mYTParents is an open-source framework for building parental control devices.
You can use mYTParents free in non-commercial or academic environments under the MIT license. Commercial use requires a commercial-use license.
The first example of a commercial use of mYTParents is YouTube Parents -- the world's first YouTube-specific internet content filter.
The easiest way to get started with mYTParents is to build your own device. A basic device is a Linux-on-a-chip device (most probably a Raspberry Pi) that you install on your network. It operates as a wireless access point -- once it's up and running, connect your child's devices to that wireless access point. The basic installation contains modules that allows a) ad hoc disable/enable of internet access, b) time access controls, and c) adult content and safe-browsing blocks. Read our Getting Started guide.
The mYTParents source code is available on GitHub: https://github.com/mytparents. Use the https://github.com/mytparents/mytparents-server repo for server-side code, and https://github.com/mytparents/mytparents-device for device-side code.