This information was written originally as a response to a post elsewhere in this forum. Since it may be of more general applicability, I have re-posted the pertinent part of the original post here for additional discussion.
Fortunately it is easy to tell if your new license is transferrable by typing Winver in the Start/Search box. Read the bottom of the license that appears.
If the license is granted to the user, it is transferable. If the license is granted to a manufacturer, it is not.
Compare these two images of licenses from two computers. (Note that the original edition determines the edition of Windows 10 licensed).
The above is a Windows 10 upgrade of a full retail copy of Windows 7 Ultimate (purchased from the Microsoft Store online).
The following is an upgrade of an OEM Windows 7 Home license on my wife's HP All-in-One purchased from HP.com.
In the first case the orignial license was granted to the user so the Windows 10 upgrader determined it is transferrable. In the second the original license was granted to HP, so the rights were not transferred to the user when Windows 10 upgraded the software. That is the legal reason the user cannot transfer it.
So there is no need to guess about transferrability. Simply use winver and read.
And just to answer another question often fumbled by helpful posters, this is the license generated by a Windows 10 upgrade to retail Windows 7 running in a VMWare virtual machine.
As you can see, it is transferrable since I own the email address. In fact my online identity is my email addy for many purposes.
So, just use the Windows 10 license generated by the Windows 10 upgrader to tell you if your license is transferrable.