One of Microsoft's most lucrative products is coming to an operating system Steve Ballmer likened to 'cancer'

Microsoft SQL Server, the company's flagship database software, has long been one of the company's most lucrative enterprise products, alongside its Windows Server operating system.

Today, Microsoft announces that SQL Server is coming to Linux - the free operating system that former Microsoft CEO Steve Ballmer once likened to "communism" and a "cancer."

SQL Server for Linux is available in a private beta today for select customers, with a full release targeted for next year, Microsoft says in a blog entry.

Linux, created in the early 1990s by incredibly influential programming firebrand Linus Torvalds and further developed by a veritable army of volunteers from around the world, never quite toppled the dominance of Microsoft Windows on the desktop.

But it's the operating system of choice in the data center, where "free" is a very important part of the equation when you're planning on installing the software on hundreds of thousands of servers. Plus, Linux provides an important part of the core of Google Android, giving it an extreme reach.

Under Ballmer, Microsoft treated Linux as enemy number one, given the threat it posed to its all-important Windows business. Microsoft had an internal "Linux compete" initiative with strategies to combat the operating system in all sorts of ways, from product to marketing.

Microsoft's current CEO, Satya Nadella, has softened his stance on Linux considerably.

Under his leadership, Microsoft has begun enabling support for Linux on flagship products like its Microsoft Azure cloud computing platform. Nadella even boldly declared that "Microsoft Loves Linux" at a press event shortly after taking command of the company. Microsoft even built its own custom version of Linux for one product.

By bringing Microsoft SQL Server to Linux, the company extends its reach into those many data centers that don't use the homegrown Windows Server platform. It'll be available for Linux virtual machines running in the Microsoft Azure cloud, and for customers to install on their own Linux servers.

It's a logical move - just not one that anybody would have ever expected from Steve Ballmer's Microsoft. And it's just another way that Microsoft CEO Satya Nadella understands that sometimes you can work with competitors so everybody can win.