I'm not sure what standard is being used to justify that claim. The power of proprietary software over the user remains a threat and Microsoft remains a chiefly proprietary software distributor. Sure, any serious analysis of the server-side computing would conclude that GNU/Linux is widely used over Microsoft Windows, but many tech people still buy into the points Ziff-Davis started and ended their pro-corporate coverage with (a list of proprietary programs Microsoft now offers to run on a GNU/Linux system and claims that "the momentum is growing"). So whatever software freedom gains were won by running a wholly-free OS are easily lost to a politically naive admin's choice of running proprietary software atop that system.
Some key distinctions are still failing to be made and for easily understandable reasons:
- Microsoft's Mark Russinovich presumably heard what Stallman said at his talk (which was said to be a "mostly standard talk"). Stallman's talk usually includes a clear description of how the free software movement he started predates the open source development methodology by over a decade and stands philosophically distinct as well (old essay, newer essay). Yet Russinovich wrote that Stallman's talk is "OSS-related" which is right in line with why the open source development methodology was started: corporate cooptation of a social movement that poses a real threat to proprietary software. That threat comes in part by challenging proprietary software's unethical underpinnings.
- ZDNet's article continues on this theme at the top and bottom of the article (as to be expected of corporate news which makes up the majority of computer news coverage and repeater/pointer sites like this one):
Each time Microsoft makes another open-source-related move these days, there are still always folks on Twitter or in comments on blog posts who caution that Microsoft hasn't really changed and never will be a true friend of open source. This change in Microsoft didn't happen overnight, but the momentum is growing.
Proprietors (including Microsoft) like "open source" instead of "free software" because open source doesn't question proprietary control over the user. Open source poses no threat to proprietary power by questioning running proprietary software on OSes that respect a user's software freedom (the freedoms to run, inspect, share, and modify published computer software).
Microsoft is much the same as it was before, only the PR campaign has changed from more honest namecalling ("Linux [sic] is a cancer that attaches itself in an intellectual property sense to everything it touches")—honest in that it betrays what Microsoft actually considers principled competition to be—to appearing warmly welcoming ("Microsoft [heart symbol] Linux [sic]"). They dare not call a complete OS GNU/Linux (which it most likely is in both quotes) because that might bring software freedom to mind (I'll bet Stallman mentioned this as this too is part of every talk he's given on this topic for many years).
What Ziff-Davis called Stallman's "distaste for Microsoft" is clearly understood by hearing Stallman's principled objections based in the facts of how computers work and an ethical examination of how we ought to treat each other with computers. But in corporate media it's necessary to downplay principled examination and explication in order to diminish the severity of the objection. After all, Ziff-Davis like virtually all other computer news coverage out there is sympathetic to "open source".
Microsoft wants users to run a GNU/Linux system as a VM on top of Microsoft's system as that helps Microsoft collect payments (licensing or rent, depending on the details of hosting) and, perhaps more importantly, spy on literally every bit of data that the user's OS deals with. Spying is big business and directly tied to proprietary control over the user. Microsoft offers a service to help users host their VM on Microsoft-owned hardware (so-called "cloud computing") too. Just to show the stark difference: Stallman, by comparison, explained what "cloud computing" actually means and why you should only run VMs on free software systems you own and control.
No, the free software movement has its work cut out for it in terms of getting people to reject proprietary software on principle and in light of how users are (by design) treated unfairly with all proprietary software. So nothing of substance has changed on that ground because ethics are too deeply rooted for any change and computing has only really altered in that more people are being offered computing services more than ever before. Software proprietors are still unmotivated by the same principles that software freedom activists are. Microsoft's change is quite superficial and PR-related. The social harm of proprietary software continues apace.