It's FOSS - https://itsfoss.com/kali-linux-debian-wsl/
Brief: Kali Linux and Debian join Ubuntu and SUSE Linux on Windows Subsystem for Linux (WSL). This means that now you can install these Linux distributions in command line mode inside Windows 10 like any other Windows application.
Last week Microsoft announced the availability of Debian and Debian based hacking distribution Kali Linux on Windows Subsystem for Linux. You can download these two distributions from Microsoft Store and install them like any other Windows 10 application. This way, you get the command line version of these Linux distributions.
These announcements should not come as surprise because Kali had already announced on their