Wine is an implementation of the Windows API on top of X and Unix. It does not require Microsoft Windows, but can use native Windows DLLs if they are available. It provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes.
minor feature: Swapchain support in Direct 3D 12. Vulkan support updated to the latest spec. Deger support for Wow64 processes. Still more support for the Task Scheduler. Various.