Microsoft yesterday open-sourced part of their WebGL renderer implementation on GitHub. Their GitHub repo contains a select number of files from the implementation of WebGL that ships in the Edge browser.
The source is provided together with tests, as a reference for engineers who are creating web browsers and related applications. By publishing this code, we hope to facilitate the investigation and resolution of any interoperability issues that may exist between different implementations of the standard.
For now they are sharing source code alone. In future, they have plans to provide project files and instructions to generate binaries down the line.