A little more clarity and information has been revealed by Microsoft about its scheme to offer Windows 10 as a free update for Windows 7 and Windows 8 users for the first year of Windows 10's availability. The company's Australian Partner Network site offers a few specifics surrounding the different editions of Windows 10 that were described last week.

We already knew that the free upgrade would not apply to Windows Enterprise customers who buy their Windows licenses through volume license agreements. The post reiterated that the free upgrade will only be available for Home, Pro, and Mobile (formerly Windows Phone) customers, regardless of whether the devices are used at home, at work, or for BYOD.

We now know how the different editions will work. Windows 7 Home Basic and Home Premium, and Windows 8 and 8.1, will all upgrade to Windows 10 Home. Windows 7 Professional and Ultimate, and Windows 8 and 8.1 Pro, will all upgrade to Windows 10 Pro. This upgrade will be free, and will be delivered exclusively through Windows Update. Corporate Windows Pro systems using WSUS will have to use Windows Update in order to use the upgrade.

The company does not appear to have spelled out upgrade eligibility for older operating systems, which means there probably isn't any, and that Windows XP and Windows Vista users will have to buy a full copy of Windows 10. System builders likewise; build a new machine and you'll need to buy a license. Windows 10 isn't free; only some upgrades to Windows 10 are free.

Once upgraded to Windows 10, devices will continue to receive both feature and security updates for what Microsoft calls "the life of the device." The reasonable inference is that updates will be delivered approximately "forever," and such an interpretation would be consistent with Microsoft's goal of avoiding platform fragmentation and ensuring that Windows developers can reach as broad an audience as possible. This would also be consistent with Windows being licensed "forever."

For Windows 7 Enterprise and Windows 8 and 8.1 Enterprise users, the upgrade to Windows 10 appears that it will work in the same way as past volume license upgrades work; the volume license will almost always be tied to a subscription, and those subscriptions already entitle subscribers to use the newest version of Windows available.

Windows RT devices will also be excluded from the Windows 10 upgrade. Microsoft has promised some kind of upgrade for owners of ARM devices such as the Surface RT and Surface 2, but the exact form this will take remains unknown.

Microsoft's current intention is that the free upgrade will only be available for the first year. After that first year, conventional boxed upgrades of the kind that Microsoft has historically used will be sold. We wouldn't be tremendously surprised to see the free upgrade extended for one reason or another, but officially it's a time-limited offer.

Windows Phone 8.1 devices will be upgradable to Windows 10 Mobile. Oddly, the blog post says that this too will be a time-limited upgrade. A little uncertainty surrounds the Windows 10 Mobile upgrade process. When announcing the Windows 10 editions, Microsoft said that it would be handling the updates for the phone platform. This led to conjecture that perhaps, at last, the platform would be free of the carrier intervention that has delayed so many updates in the past.

Unsurprisingly, further "clarifications" since then have said that the carrier involvement is not being eliminated. As such, the Windows 10 Mobile update process is likely to be essentially identical to the Windows Phone 8.1 process, with all the frustrations this implies. The company did publicised a plan at WinHEC earlier this year, codenamed Project Milkyway, to ensure that users receive each update with 4-6 weeks of its release, but this is merely a goal and not a concrete promise.

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