Microsoft Makes 'Roslyn' Compiler Open Source

Also announced was a new interop organization called The .NET Foundation.

Microsoft Technical Fellow and coding legend Anders Hejlsberg looked down at his display, where the large button titled "Publish" lay underneath his finger. He pushed the button, which was linked to a project on CodePlex. With that, he announced "Roslyn is now open source!"

Huge applause from the audience at Build 2014 followed. With that push of a button -- live onstage during the Day 2 keynote -- Microsoft took what many believe is a giant leap forward in the world of interoperability.

"Roslyn" was the code name for Microsoft's .NET Compiler Platform. Hejlsberg's action opened up the C# and Visual Basic compilers as APIs, giving developers access that would have been unheard of from Microsoft just a few years ago.

It was the highlight of a keynote that demonstrated Microsoft's drastic shift from being a proprietary code company to one of the most cross-platform-friendly companies in the industry.

In addition to open sourcing Roslyn, Microsoft also announced a new organization for open sourcing technology: the .NET Foundation. "The .NET Foundation will be the steward of a growing collection of open source technologies for.NET, Microsoft's comprehensive development framework," states the homepage of the Web site.

The Foundation kicks off with 24 .NET Framework open source projects, including Roslyn. Other projects on that list include:

  • Entity Framework
  • ASP.NET SignalR
  • Managed Extensibility Framework (MEF)
  • Windows Azure .NET SDK
  • .NET Map Reduce API for Hadoop

The Foundation emphasized the involvement of Miguel de Icaza, CTO and co-founder of Xamarin, which allows developers to use C# to build apps for iOS and Android devices. Also listed as participants in the Foundation were Laurent Bugnion (IdentityMine), Niels Hartvig (Umbraco), Nigel Sampson (Compiled Experience), Anthony van der Hoorn (Glimpse) and Paul Betts.

Eric Lippert, a former Microsoft employee who served as a principal developer on the C# compiler team and a member of the C# language design team, stated on his blog that Microsoft's license terms for Roslyn demonstrated Microsoft's commitment to this new openness. "What astonished me was that its not just a "reference" license, but a full on liberal Apache 2.0 license."

The .NET Compiler Platform can be found here.


About the Author

Keith Ward is the editor in chief of Virtualization & Cloud Review. Follow him on Twitter @VirtReviewKeith.

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