To clarify:

The code involved in the leak isn't the whole of Windows 10, but apparently it does contain a bunch of drivers and kernel components. So far as I'm aware, it's a kit designed for trusted companies that have device driver development teams, and contains special debug/testing builds alongside with reference sources and testing tools.

This does not matter, however: it's still illegal to obtain that leaked data, and it will effectively ban anyone who has read it from contributing, the same as with any other leak, past or future.