It’s a big day for Microsoft and its (soon to be even larger) cadre of dedicated developers: Starting today, Microsoft is making the core parts of its .Net framework open-source, and cross-platform on Windows, Mac OS X, and Linux. Microsoft is also committing to adding Android and iOS support in the upcoming Visual Studio 2015 — in fact, there’s already an Android emulator in Visual Studio 2015 Preview, and iOS support will be added soon. Furthermore, Microsoft is releasing a new version of Visual Studio — “Community 2013” — that is free and full-featured. This is a bold move that will attempt to cement .Net, C#, and Visual Studio as the dominant development platform across Windows, Linux, Android, iOS, and Mac — and, well, it might just work.

Over the last few years, Microsoft has been slowly open-sourcing various parts of its developer tools, mostly in response to the fact that developers expect a lot more transparency than they used to. It didn’t make much sense to open-source stuff when Windows was the only OS that mattered, but the rapid growth of Linux as a server platform, and Android and iOS in the consumer space, have forced software developers to take a much broader, platform-agnostic stance — and Microsoft has followed suit. It’s actually been quite amusing and heartwarming, watching Microsoft go from hating everything about Linux and what it stands for, through to positively embracing the penguin.

Anyway, today Microsoft is open-sourcing the .Net Core framework. You can download it (and Microsoft’s other open-source goodies) on Github. Basically, prior to this point, you could only run .Net apps properly on Windows desktops and servers — you had to use a third-party runtime called Mono if you wanted to run .Net on Linux, Mac, iOS, Android, or any number of lesser-known OSes. Mono is a valiant effort, but there’s no getting around the fact that the original, first-party .Net is far superior. Now, with .Net being open-sourced, these other platforms should all (soon) be able to run .Net applications perfectly. You might even say that this will soon make .Net as useful as Oracle/Sun’s Java Virtual Machine…

Furthermore, Microsoft has announced that Visual Studio 2015 will be “built from the ground up with support for iOS, Android and Windows” — as opposed to just Windows. The Preview release of Visual Studio 2015 already has a full-featured Android emulator baked in. I’m not sure what’s planned for iOS, but presumably Microsoft wants to offer an alternative path to Xcode and Objective-C/Swift with Visual Studio and .Net/C#. In addition, if you’re a student or an open-source developer, Microsoft has also released a free and full-featured Visual Studio Community edition for you to play with.

Along with these releases, Microsoft is also committing to developing .Net in the open — it’s one thing to just dump a ton of .Net code on Github and let people with it, and quite another to listen to the community and push new updates on a regular basis.

Overall, these are some very bold moves by Microsoft — but also necessary moves, if Microsoft wants to stay relevant in a world where the blunt club of Windows no longer has the terrifyingly hefty clout that it once had. C#, .Net, and Microsoft’s myriad other developer tools are top-notch. There will be a lot of excited iOS, OS X, Android, and Linux developers today.

Now read: Microsoft releases free Office apps for iPhone and iPad, Android coming soon