That's right--Microsoft is offering a fully-functioning, non-expiring copy of Windows 10 via download at no cost *. Reserve your copy now and when it's released (July 29), they'll download it to you. You can cancel the reservation with no penalty at any time. For more including how to reserve:
The real deal and both are safe links.
* They don't say so explicitly but I assume they will DL to as many individual computers as you have, and to anywhere in the world.