Reaction to Microsoft’s announcement yesterday that it was giving up its .NET Core to open source has been swift, and largely positive.

Almost as telling as the reaction to the technical portions of the announcement was the reaction to Microsoft’s decision to open-source the .NET stack and enable it to run on Linux or Mac OS platforms.

(Related: Microsoft’s big .NET announcement)

Al Hilwa, program director of software development research at industry analysis firm IDC, tweeted: “#spacecraft lands on #comet, #Microsoft open-sources #dotnet, #VisualStudio to support #Linux & #iOS – Pigs to fly!”

Forrester Research analyst Jeffrey Hammond wrote in a note to his clients: “We’ve now come 180 degrees from Microsoft execs attacking Linux (and open source) as a ‘cancer.’ And it wasn’t that long ago that pitched battles were fought inside the halls of Redmond over cross-platform (i.e., anything but Windows) support.”

Jim Zemlin, executive director of the Linux Foundation, lauded the announcement, but noted begrudgingly, “We do not agree with everything Microsoft does, and certainly many open-source projects compete directly with Microsoft products. However, the new Microsoft we are seeing today is certainly a different organization when it comes to open source.”

Microsoft corporate vice president of the developer division Soma Somasegar said in a Monday interview with SD Times that in a mobile-first, cloud-first world, “developers are center stage.”

In his blog, Zemlin pointed out that Microsoft has always understood that developers are “masters of the universe (at least in the software world),” and added, “Open source has fundamentally altered the software industry and that puts developers…in charge.”

Zemlin estimated that 80% of a stack is made up of open-source software and 20% is custom, proprietary software. “As a result, companies and individuals are hustling to understand how to harness collaborative development to advance new technologies and transform markets,” he said.

IDC’s Hilwa called Microsoft’s announcements “huge” and “a real win and a shot in the arm for the Microsoft developer ecosystem. There has been a lot of demand for Visual Studio to support other platforms and other development ecosystems, especially running on the Mac and supporting iOS development. That so much of the developer and middleware stack is going open source is certainly a sign of a fast-transforming Microsoft.”

In his note, Forrester’s Hammond pointed out that today’s Microsoft is less about Windows, as the company can no longer afford to ignore consumers that don’t use Windows, or developers that don’t deploy on it. He also pointed out that open-sourcing .NET and embracing Linux “puts the Azure team on an equal footing with key competitors like Amazon, Google and IBM.”

Hammond added, “The changes shatter .NET’s status quo as a Windows-only developer framework,” so Microsoft can hold onto its .NET developers deploying to other platforms and attract new developers as well.