If there's ever been a great opportunity to open source something in the Windows client, it's WSL. A number of popular User Voice feature requests were closed recently as not in scope, which is reasonable on the part of the WSL team but shows that the demand for Linux-on-Windows is much greater than the team's current objectives. If the project was open source and the team accepted patches who knows where this thing could go. People want to run X, they want device emulation, they want to run all kinds of apps that aren't necessarily dev tools.