Okay so how I read it is that as long as I upgrade from Windows 7 to Windows 10 during it's first year of availability it is free. If I choose to upgrade after that I would have to pay.
If I am wrong would someone please correct me. Sometime I do try to make things more difficult then they are. If I'm correct that would be hard to pass up.
1. It will be free on any machine (W7, W8.1) as an upgreade (not clean install).
2. If for any reason you change your mobo (perhaps even processor) on that machine, you will have to buy a W10 license.
3. It won't be sold as a subscription (i.e. the Adobe software model). (http://www.pcgamer.com/microsoft-windows-10-will-not-be-sold-as-a-subscription/)
Also:
"It is very clear from this post that for the first year it's available, you can upgrade to Windows 10 for free if you have Windows 7 or 8. You will not pay for it. After that year is up, nothing will happen to your Windows 10 license. If you do not upgrade within that year, however, you will have to pay for an upgrade. The offer expires after a year, not the upgrade."