Other Implementations
The Wine project is an attempt to provide a Win32 API compatibility layer for Unix-like platforms. ReactOS goes a step further and aims to provide an implementation of the entire Windows operating system, working closely with the Wine project to promote code re-use and compatibility. DosWin32 and HX DOS-Extender are other projects which emulate the Windows API allowing the execution of simple Windows programs from a DOS command line. Odin is a project to emulate Win32 on top of OS/2.
Windows Interface Source Environment (or WISE) was a licensing program from Microsoft which allowed developers to recompile and run Windows-based applications on UNIX and Macintosh platforms. WISE SDKs were based on an emulation of the Windows API that could run on Unix and Macintosh platforms.
Read more about this topic: Windows API