From the last two publications that concern free of charge ή not available of Windows 10 clearly seems to be confusing in the Microsoft Licensing section. But let's look at the sequel because history does not end here.
In Licensing each product there are the license agreements, drafted by Microsoft's large legal teams, with separate terms for PC manufacturers and end users. 
These terms co-exist are very specific rights and responsibilities from each party to the license agreement.
They are mainly targeted at Microsoft's professional clients, PC makers, and company partners, who represent more than 98 percent of total Windows license revenue.
But there are also unwritten rules. Intended for hobbyists, Windows enthusiasts, and professionals information technologys who like to experiment with Windows and their computer hardware. Microsoft's TechNet program has been a long-term gift to this group, offering thousands of dollars in Microsoft software for very cheap.
The Windows program Insider seems to follow the same spirit.
Every time Microsoft makes a public statement silently (and carefully) validates unwritten rules. This was also the case this week, with the announcement in the official Microsoft blog that wanted Windows to come for free for all registered members of the Microsoft Windows Insider program:
Windows Insiders running the Windows 10 Insider Preview (Home and Pro editions) with their registered MSA connected to their PC will receive the final release build of Windows 10 starting on July 29th. This will come as just another flight. I've gotten a lot of questions from Windows Insiders about how this will work if they clean installed from ISO. As long as you are running an Insider Preview build and connected with the MSA you used to register, you will receive the Windows 10 final release build and remain activated. Once you have successfully installed this build and activated, you will also be able to clean install on that PC from final media if you want to start over fresh.
What you will notice if you read the paragraph above carefully is that it does not contain any legal language. In fact, the word license (license) does not appear anywhere in the text.
Update first June 21: Via Twitter, Verge's Tom Warren notes that the publication changed overnight by adding and removing text to activate. In the following text you can compare the changes: 
These changes, of course, only confused, as the legal terms were clearly added to the description. In fact, the latest proposal runs counter to everything that precedes it.
According to ZDNet, however, we had developments:
Update second, 21 June 24: 15 PDT: On Twitter today, one day after the changes, Microsoft's Gabe Aul confirmed that registered Windows Insiders who upgrade from a clean installation of the preview version will end up with a fully-powered copy of Windows 10.
It is no coincidence that this post makes no reference to the Windows license. Instead, it is a reflection of the fact that the unwritten rules must finally be written.
Thus, with an eye closure and a nod, people who are not PC makers or part of a business network will be able to:
Yes, anyone who signs up to the Windows Insiders program and install a preview build will receive the final version automatically, without any hassles and no activation required.
Yes, this copy of Windows 10 will remain enabled, even if it was installed clean (by ISO) without traces of a previous version of Windows.
Yes, you will be able to perform a clean installation of Windows 10 on this PC by official media (ISO) if you want to start from the beginning
And although there is a technical conflict with the terms of the license, you can relax. Microsoft is pleased to have included you in the Windows team.
Why is Microsoft doing so? I can think of a billion reasons.
Microsoft's declared goal is to put Windows 10 on a billion devices for the first three years after their release. To reach this huge number, it has to convince hundreds of millions of current Windows users to upgrade.
Asking people to pay for sure will hear a lot not. So the upgrading will be free for the vast majority of today's PC users.
You could think of it as a reward for the millions of users who have taken part in the Windows Insider program, but there is really a much more practical reason:
It's just not possible to make any kind of license for personal computers, and any attempt to do so will only cause friction. Likewise, any activation requirement will cause friction.
Friction means that there will be too many disappointed and will cancel the upgrading. With friction it will not be able to catch the target of one billion Windows 10 in the coming years.
So why not say, "Windows 10 is free"?
Businesses will still need to pay for Windows Enterprise licenses. PC makers will still have to pay for their OEM copies.
License terms for a new version of Windows do not usually appear until the last minute. Generally, however, they rarely change, but Redmond's lawyers wanted to add their own touch to the company's initial publication.
