It sounds like another one for the Hell Freezes Over file: Microsoft has released a version of FreeBSD 10.3, an edition of the liberally licensed Unix-like OS.
But as with previous Microsoft dalliances in the world of open source-licensed OSes, this isn't a case of Microsoft admitting Windows is a technological and philosophical dead end. Instead, it's an example of Microsoft's continued effort in strengthening Azure's appeal as an environment to run such OSes.
The details are simple: FreeBSD 10.3, the latest production version of the OS, is available as a download-and-go VM image in the Azure Marketplace. This image, however, has Microsoft, not FreeBSD Foundation (the organization that supports FreeBSD development) listed as the publisher.
What's new about Microsoft's particular spin of FreeBSD? A post on the Microsoft Azure blog notes that it sports kernel-level improvements to improve network and storage performance, as well as the "Azure VM Guest Agent" that allows FreeBSD to talk to Azure Fabric and vice versa. There have been Linux kernel contributions by Microsoft in this same vein; they were designed to allow Linux to run well on Hyper-V.
A slightly new wrinkle is Microsoft's non-Azure-centric contributions to FreeBSD. Those changes, according to Microsoft, are being upstreamed back into FreeBSD, "so anyone who downloads a FreeBSD 10.3 image from the FreeBSD Foundation will get those investments from Microsoft built in to the OS." In other words, the changes in the Microsoft-published, Azure-hosted FreeBSD aren't an Azure exclusive -- all FreeBSD users will benefit in time.
Microsoft lends a helping hand
The other question people are likely to ask is why, kernel contributions notwithstanding, is Microsoft listed as the publisher of the distro? The short answer: support.
According to Microsoft's blog post, the FreeBSD Foundation is a community of mutually supportive users, "not a solution provider or an ISV with a support organization." The kinds of customers who run FreeBSD on Azure want to have service-level agreements of some kind, and the FreeBSD Foundation isn't in that line of work.
The upshot: If you have problems with FreeBSD on Azure, you can pick up the phone and get Microsoft to help out -- but only if you're running its version of FreeBSD.
Another incentive for Microsoft is that FreeBSD is used as the substrate for virtual appliances from a number of name vendors -- such as Citrix and Gemalto. Microsoft wants those products to run on Azure, too, and has worked closely with their vendors to ensure that. Microsoft is also hinting this is a prelude to not only more Hyper-V features in FreeBSD, but more kernel-level performance contributions generally.
Microsoft has so far produced only one item resembling a distribution of an open source OS: Azure Cloud Switch, a Linux distro designed for ASIC hardware to run Microsoft's network management software. It hasn't been made available for public use (it was built mainly for Microsoft's own internal use at Azure), so don't hold your breath waiting for it to appear on GitHub.
Microsoft's direct contributions to other operating systems have inevitably revolved around making them more compatible with its own ecosystem. Even the new, Nadella-driven Microsoft, which is far friendlier to open source, isn't likely to veer far from the course. But if it means an incrementally better FreeBSD for all, it's hard to complain.