The Insider Branch is Microsoft's ultimate guinea pig crowd, that will, it hopes, identify problems and suggest changes before the rest of the Windows ecosystem gets them.
Microsoft's decision to give away Windows 10, even to those not eligible for the free upgrade — those running Windows 7 Starter, Home Basic, Home Premium, Ultimate and Professional, as well as Windows 8.1 and Windows 8.1 Pro — and tie it to remaining in the preview program may have been planned. Or it may not; it's hard to tell sometimes.
In any case, Microsoft has made much of Insider the test pool for detecting issues, problems and flat-out failed updates before they're handed to others, including the bulk of consumers, who will tap into Current Branch. The more Insiders, within reasonable limits, the more data Microsoft will receive from its canaries.
Microsoft receives considerable information from Insiders, whether they explicitly provide feedback or not: By default, Windows 10's preview sends what Microsoft calls "full health, performance and diagnostics" data to Redmond. (The full list disclosed by Microsoft is here.)
The move could also be read as yet another tactic in Microsoft's pledge to put Windows 10 on a billion devices within three years, although the number who will leverage the loophole will be infinitesimal compared to the volume of users who will upgrade via the one-year offer. Still, every little bit helps.
On the other hand, by limiting the free-for-anyone carrot to those who stick with Insider, Microsoft has deftly limited it to hobbyists who won't mind being on the bleeding edge. Any business user who stayed with Insider on a production device would be certifiable.
Microsoft's latest to-and-fro over who gets Windows 10 free and who has to pay is reminiscent of the botched messaging earlier this year, when the company first said that pirated copies could be upgraded to legitimate versions of Windows 10. Days later the company walked back that statement, saying that the free Windows 10 upgrade offer "will not apply to non-genuine Windows devices."
It also illustrated how differently Microsoft defines "free" than does its desktop OS rival Apple.
Since October 2013, Apple has given away OS X upgrades to any owner of an eligible Mac. It doesn't matter where that Mac is used — at home, in college, at work — or what version the user was previously running. (Of the latter, Apple does have limits — the earliest edition able to upgrade for free has been 2007's Snow Leopard because that's the oldest to support the Mac App Store, from which the upgrade is delivered.)
Microsoft, on the other hand, bars users of Windows Enterprise, the widely-used corporate SKU obtained via a volume license, from the free upgrade. It also blocks Windows Vista — the 2007 OS whose code base is very similar to Windows 7's — from the deal.
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