Darwin subsytem for Linux. Not actually a subsystem like WSL, but runs an Ubuntu 16 VM on a hypervisor (xhyve or hyperkit) and adds a nice frontend to manage the VM. Goal is to make running Ubuntu or any flavour of linux as seamless as possible using existing technologies.
Head over to releases page to download the latest version of Ubuntu.dmg and move the App to Applications folder. On the first run, it will make you download a base image, which is 3 Gb in size. You can later make and attach other disks to the VM. Login via SSH using username default and password password.
We do not own the Ubuntu image - the hosted base image is derived from Ubuntu Server 16.04.5 and Canonical Ltd. is the rightful owner of Ubuntu. Please open an issue if this needs a proper licensing.