Microsoft released Windows 10 IoT Core Insider Preview which supported embedded devices including Raspberry Pi 2, Arduino, MinnowBoard Max, Galileo and several other.
Folks who want to give Windows 10 for embedded devices can do so with Windows 10 IoT Core Insider Preview which is a free download for testing purposes only.
To download Windows 10 IoT Core Insider Preview, you need to have Github and Windows 10 Insider account, then take a survey before being taken to the download page.