Microsoft explained to confusion with the free Windows 10 for insiders
With the second and last (I hope) update its publication on June 19, Microsoft has removed all doubt on the topic of «Insiders Vs. free Windows 10».
In a few words, if you joined the Insider program and do not intend to leave, you are entitled to a free copy of Windows 10, regardless of whether you have a genuine license to one of the two previous versions of the operating system or not.
Obviously, there is one «but». You will be an insider. This means that your copy of the operating system will always be a part of the program Windows Insider. And as all versions produced in the framework of this program, have a certain validity, you will have to install all previews of future updates released by Microsoft after July 29. Otherwise, the period of activation your copy of Windows 10 ever expire.
In short, if you don’t mind to be a free tester, you will receive a new operating system for free indefinitely. At the same time, you will have to deal with advanced and potentially unstable versions, but the choice is yours. Fortunately, Microsoft will provide ISO these builds, so if anything you’ll be able to reinstall the system from scratch.