Microsoft announced that it is releasing the .NET Core Runtime and libraries as open source code under an MIT license. Microsoft VP for Cloud and Enterprise Scott Guthrie writes in his blog that Redmond is open-sourcing the .NET Core Runtime, which includes “the CLR, Just-in-Time Compiler (JIT), Garbage Collector (GC), and core .NET base class libraries.”
The news follows a series of earlier announcements this year, marking a significant shift in the company’s relationship with the world of open source. In April, Microsoft launched the .NET Foundation, a non-profit group that would guide future development of .NET technologies. Leading open source developer (and creator of the Mono framework) Miguel de Icaza was even added to the .NET Foundation board. Also, the company has recently open-sourced code for ASP.NET, EF, Web API, NuGet, and the "Roslyn" C# and VB compilers.
 
The recent moves to embrace open source should help build better collaboration between Microsoft and community-based programmers. The company is also hoping that eliminating restrictions on the use of its technologies will lead to more widespread acceptance. As many commentators have pointed out, Microsoft has significantly changed its stance on open source since 2001, when then-CEO Steve Ballmer called Linux “… a cancer that attaches itself in an intellectual property sense to everything it touches.” But actually Redmond figured out it couldn’t squelch open source software several years ago, and the change to better cooperation has been gradual. Acceptance picked up steam when Satya Nadella took over as the new Microsoft CEO; he even appeared recently beneath a giant projection of the words “Microsoft” and “Linux,” with a big red heart between them to affirm that “Microsoft Loves Linux.”