Microsoft has open sourced Project Islandwood, a new tool for converting iOS apps to Windows 10. The tool is now available at GitHub, where it is called WinObjC. At this point, Project Islandwood is still an early preview rather than a finished product; the final version is due for release this fall.
At its Build conference, Microsoft announced plans to release four "bridges," including Project Islandwood, that would make it easier to port applications built for other operating systems to Windows 10. The others are Project Westminster, which brings Web apps to Windows; Project Astoria, which brings Android apps to Windows; and Project Centennial, which updates existing .NET and Win32 apps for the Windows Store.