New
#40
No. That was never true and still isn't.
If you have a retail license you can use it as you wish. I don't know anything about OEM but Windows 10 works the same as 7 for retail licenses (i.e. you have to call them if the hardware changes).
You can (and I have tested this) still use your old windows 7 key to activate 7 or 10 (version 10565)
You can (and I have tested this) activate 10565 with a valid earlier key and then clean install 10240.
You can (and I have tested this) restore your old version (7 in my case) and it is still activated.
The idea is that you are either licensed or not. You are licensed on your machine for 10 if you either had licensed insider preview before RTM in June or if you have a valid legacy (7 or 8) version or you bought a Windows 10 key.