Windows 10 Free Upgrade - What happens to Windows 7/8?

Microsoft is giving Windows 10 away for free to Windows 7/8/8.1 users. If one reserves Windows 10 with the new notification in the tray area, what will happen to their Windows 7/8/8.1 license?

Are you really getting Windows 10 for free, as in you upgrade from 7/8/8.1 but you still own the previous version of Windows and Windows 10, or are you really trading your old Windows license for a new one?

Basically, after upgrading to Windows 10 for free from Windows 7, will I still own Windows 7? (Will the product key for 7 still work?)

It is absolutely clear. After you have upgraded, there is no downgrade "right" though doubtless you can continue on 7/8 at least for a while.

Certainly if you are asking will the 7/8 license ALSO be valid at the same time - it will not. It is replaced entirely.