Just incase anyone was wondering, you don't have to give any email address. It'll ask for one, so it can notify you of the launch date. And there's a checkbox (unchecked by default) asking to spam you with other Microsoft offers, but this is all optional.
My computer "reserved" Win10, and said, "Great, you're reserved!" (or something similar), and the email page is the page after you've already reserved, for notification, and there's also a subtle link saying "Skip Email Notification". Clicking it does what it says on the tin.
The email notification is pretty silly anyway, since if you "Skip Email Notification" it says "You'll get a notification on your PC or tablet when Windows 10 is ready for you".
Despite "reserving" it (giving Microsoft permission to pre-load it on my computer without installing it), I'm probably going to wait a week or two post-release before I install it.
Also, for those asking, there are six versions of Win10, not just Home and Pro - you can look up the details if you like, but from memory I think it was: Home, Pro, Mobile, Business, Business-Mobile, and Education.
They keep marketing things like "Free Upgrade for the first year". Followed up by "It is not a subscription!"
I was worried about that as well, but they did eventually clarify that part. For the first year, it costs you zero to update. i.e. it's the equivalent of saying "This offer is only valid for the first year". Too lazy to look up the links I read.
Microsoft is fairly bad at explaining to the public what they are doing. For example, their XBone digital distribution strategy that they had to eventually cancel, because all they were able to successfully communicate was that they were using DRM to block people from selling their game discs.
Or "Once a Windows device is upgraded to Windows 10, we will continue to keep it current for the supported lifetime of the device –at no additional charge." ... but who decides what the "supported lifetime of the device" is? Supported lifetime is tricky. They're still selling Windows 7 on OEM computers yet mainstream support officially ended five months ago. Windows 7 is past its "supported lifetime" but still a very active commercial product.
Yeah, that's the sticking point for me. The key part is the supported lifetime of "the device" - is that Dell/HP's limited 2 year warranty?
Personally, I think they are trying to say that, if Microsoft is releasing annual-ish Win10 upgrades (i.e. 8.0 -> 8.1), you can't get all those upgrades for free forever, but after ~2 years, the future upgrades may start costing you ~$20 or some such. i.e. if you buy a device with Win10.2 installed, you'll eventually get Win10.3 and Win10.4 for free, but Win10.5 and Win10.6 and so on may charge you. But you can choose to not upgrade, and still continue to get Windows security updates and such for your current version, until Microsoft cancels support for Win10.4.
That's speculation on my part.
It also possibly explains their "for a year" offer. They are giving free upgrades to Win10.0, but when Win10.1 releases in a year, if you're still on Win7 or Win8.1 you'll have to upgrade to Win10.1, either for free or for a fee. They don't want to imply that you can stick with Win7 for five more years and then upgrade for free to Win10.5.
I'm suspecting they mean: "If you're on Win7 or Win8.1, you can upgrade to Win10.0 ... until we release Win10.1.". Then they'll probably drop the Win7 free upgrade path, and let Win8.1 users upgrade to Win10.1 for free until Win10.2 is released, and etc...
More speculation.
That makes it tricky to deal with this: "Right now we're releasing Windows 10, and because Windows 10 is the last version of Windows, we're all still working on Windows 10 ... Windows will be delivered as a service bringing new innovations and updates in an ongoing manner", releasing Windows 10.1, 10.2, and so on, rather than Windows 11.
So by their logic, our grandchildren may be using Windows 10.3412 since Windows 10 is the last version. Just don't expect that version of Windows 10 to run on today's hardware.
Sounds like OSX. Released in 2002, we're now 13 years and ~10 updates later.