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Microsoft today announced plans to open source .NET, the company’s software framework that primarily runs on Windows, and release it on GitHub. Furthermore, Microsoft also unveiled plans to take .NET cross-platform by targeting both Mac OS X and Linux.

In the next release, Microsoft plans to open source the entire .NET server stack, from ASP.NET 5 down to the Common Language Runtime and Base Class Libraries. The company will let developers build .NET cloud applications on multiple platforms; it is promising future support of the .NET Core server runtime and framework for Mac and Linux.

S. Somasegar, Corporate Vice President of the Developer Division at Microsoft Corporation, explained the move to VentureBeat very simply: open sourcing .NET would help “get more developers onto the platform” as well as “let existing .NET developers target more users.”

This is a long-term bet. Somasegar also hinted that taking .NET cross-platform would help the company partner with additional platform and tools vendors across the industry, and eventually grow the .NET ecosystem.

The move is being implemented and supported by Microsoft, but the company had help. The new version of .NET was developed as open source in close collaboration with the Mono project and community.

For context, Mono is an open source implementation of Microsoft’s .NET Framework. The end goal for Microsoft and the Mono group is to jointly deliver an open-source, enterprise-ready .NET server implementation to Windows, OS X, and Linux.

Microsoft says the implementation will provide “a full stack for the server including runtime and class libraries and will be part of the .NET Foundation.” If you’ve been reading in shock until now, this is exactly the point where a light bulb should go on above your head.

At its Build conference in April, Microsoft announced that it was open sourcing 24 of its .NET libraries and related technologies. That’s when it created the .NET Foundation, a group for overseeing its open source .NET components. Now the foundation has received its biggest task yet: over the next several months, it will be open sourcing the remainder of the .NET Core Runtime and .NET Core Framework.

Today’s move is therefore the next logical step, although it feels more like a full sprint. To any developer who has ever written code using Microsoft technologies, it may be a bit of a surprise. Nonetheless, Microsoft is urging interested developers to join and participate in these projects by visiting the .NET Foundation website and its related repositories.