At its Build 2015 developer conference today, Microsoft took the first step toward a cross-platform version of .NET, the company’s software framework that primarily runs on Windows: The company has released a preview of the .NET Core runtime distribution for Mac and Linux.

Today’s preview is the first public version of “a solution that we think is going to be exciting to a broad set of developers,” S. Somasegar, corporate vice president of the developer division at Microsoft, told VentureBeat. “This is one of the most progressive things that we’ve done.”

Microsoft also announced the availability of the full .NET Framework 4.6 RC and the .NET Core 5 Beta 4. Yet the bigger story is that Microsoft is finally delivering on its vision to let developers build cloud applications on multiple platforms using .NET. While .NET Core OS X and Linux is implemented and supported by Microsoft, it is developed under an open-source license.

In November, Microsoft not only announced plans to open-source .NET, but also to take .NET cross-platform, targeting both Mac and Linux. Specifically, Microsoft promised future Mac and Linux support in the .NET Core server runtime and framework.

At the time, Somasegar 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. And Microsoft has help: The open-source work is being done in close collaboration with the Mono project and community, which have long been working on making it possible to run Microsoft .NET applications cross-platform.

Somasegar told VentureBeat that over the past five months, the two groups have exchanged a “tremendous amount” of ideas and code. So we asked the obvious: Why bother developing two different implementations?

“If you talk to the key stewards of the Mono community, I think they would love for us to work together as opposed to work on two independent things,” Somasegar said. He added that Microsoft wants to see where it might be able to converge with Mono’s work, but in the meantime, Somasegar reiterated: “We are committed to .NET development in open source, and we are committed to taking .NET cross-platform.”

“I’m a patient guy, so I’m willing to wait.”

Regardless of what happens with Mono, developers can now install and try the .NET Core support for Mac and Linux. Microsoft also hopes they might get involved in the associated open-source project.