According to sources at Canonical, Ubuntu Linux's parent company, and Microsoft, you'll soon be able to run Ubuntu on Windows 10.
This will be more than just running the Bash shell on Windows 10. After all, thanks to programs such as Cygwin or MSYS utilities, hardcore Unix users have long been able to run the popular Bash command line interface (CLI) on Windows.
With this new addition, Ubuntu users will be able to run Ubuntu simultaneously with Windows. This will not be in a virtual machine, but as an integrated part of Windows 10.
The details won't be revealed until tomorrow's morning keynote speech at Microsoft Build. It is believed that Ubuntu will run on top of Windows 10's recently and quietly introduced Linux subsystems in a new Windows 10 Redstone build.
Microsoft and Canonical will not, however, sources say, be integrating Linux per se into Windows. Instead, Ubuntu will primarily run on a foundation of native Windows libraries. This would indicate that while Microsoft is still hard at work on bringing containers to Windows 10 in project Barcelona, this isn't the path Ubuntu has taken to Windows.
That said, Canonical and Microsoft have been working on bringing containers to Windows since last summer. They've been doing this using LXD. This is an open-source hypervisor designed specifically for use with containers instead of virtual machines (VMs). The fruits of that project are more likely to show up in Azure than Windows 10.
It also seems unlikely that Ubuntu will be bringing its Unity interface with it. Instead the focus will be on Bash and other CLI tools, such as make, gawk and grep.
Could you run a Linux desktop such as Unity, GNOME, or KDE on it? Probably, but that's not the purpose of this partnership.
Canonical and Microsoft are doing this because Ubuntu on Windows' target audience is developers, not desktop users. In particular, as Microsoft and Canonical continue to work more closely together on cloud projects, I expect to find tools that will make it easy for programmers to use Ubuntu to write programs for Ubuntu on the Azure cloud.
So is this MS-Linux? No. Is it a major step forward in the integration of Windows and Linux on the developer desktop? Yes, yes it is.