Once again, Microsoft is offering more clarification on how the free upgrade to Windows 10 process will work for Windows Insiders. As previously stated, Microsoft says that Windows Insiders will upgrade for free to Windows 10 beginning on July 29th, but it’ll be just another build for Insiders, which means that those wanting to join the Insider program with the purpose of scoring a free license will not get a free copy of Windows 10.
Because the software maker will continue with the Windows Insider program, those people already in or want to join the program will keep getting new builds through the Fast or Slow ring of updates.
This pre-release of Windows 10 will remain activated using a pre-release product key. In addition, each new build that Microsoft releases will expire after certain amount of time, but the company will keep releasing new builds before they expire, and the new builds will continue to be activated in the same way.
All this means that, yes, Windows Insiders will upgrade to the final version of Windows 10 for free, but it will continue to be a pre-release of the operating system and you will not technically be getting a new Windows 10 license for free.
Now, if you decide to opt out of the Windows Insider program, the upgrade process will still be subject to the terms and conditions of the Microsoft offers, which states that you can upgrade for free to Windows 10, if you’re running a genuine copy of Windows 7 Service Pack 1 or Windows 8.1 Update — the offer excludes Windows XP, Windows Vista, and Enterprise version of the operating system. “This is not a path to attain a license for Windows XP or Windows Vista systems.” — Microsoft says.
This is not a path to attain a license for Windows XP or Windows Vista systemsTweet Quote
More importantly, the company explains that if you upgraded to the preview running a genuine version of Windows 7 or Windows 8.1, after you upgrade to the final version of Windows 10 on July 29th, the operating system will remain activated.
If you have performed a clean installation of Windows 10 preview, you’ll need to roll back to the previous operating system and the upgrade, or you’ll need to buy a new Windows 10 license. “If you do not roll back or acquire a new license the build will eventually expire.”
Basically, if you stay in the Windows Insider program, you will get Windows 10 for free, but with a pre-release version that it’s subject to expire, it might also contain more bugs, and it is what Microsoft will use to perform A/B tests.
Source Microsoft