Microsoft gave away some nice freebies at today's Build conference in San Francisco - including an Xbox One and $500 Windows Store gift certificate - but Redmond will also be giving away Windows licenses for smartphones and tablets less than 9 inches.
The move means phone makers will be able to produce Windows Phone devices and small Windows-based tablets without having to pay Microsoft a per-device licensing fee.
"To drive adoption of your applications and get your applications out there for more customers, on phones and tablets with screen sizes less than nine inches we are making Windows available now for zero dollars," Terry Myerson, executive vice president of Microsoft's operating systems group (pictured), said during the developer conference.
The move is a big switch for Microsoft, which has made billions by licensing its Windows software. But this offer doesn't cover its lucrative Windows desktop software, but rather the struggling mobile version.
Windows Phone has made some gains, particularly overseas, but is often a distant third or fourth behind iOS and Android when it comes to mobile OS market share. And so many phone makers must decide whether to stick with what works - Android - or take a chance and pony up for Windows Phone licenses.
Dropping that financial requirement, however, could prompt more phone makers to experiment with Windows Phone - and more developers to create apps and services for the platform.
Microsoft also talked up a version of Microsoft for the "Internet of Things" - or Internet-connected devices you might not normally think of needing Web connectivity. Myerson, for example, showed off a Windows 8.1-based piano.
But when the version of Windows for the Internet of Things comes to fruition, it will also be "available for zero dollars," Myerson said.
To make sure developers don't have to create too many versions of their apps, meanwhile, Microsoft also announced universal Windows apps.
"Since universal Windows apps run on the same Windows runtime, developers have a common way of building and architecting apps for phones, tablets and PCs; from how they handle suspend and resume and do background processing, to the way they manage in-app security," Microsoft said in a blog post.
To help get developers started in Windows Phone 8.1 and Windows 8.1 Update, Microsoft released Visual Studio 2013 Update 2 RC.
For more, check out 8 Things You Need to Know About Windows 8.1 Update, as well as Is Microsoft Backtracking With Windows 8.1 Update?