WinObjC? Windows Bridge for iOS (previously known as ‘Project Islandwood’).
Windows Bridge for iOS (also referred to as WinObjC) is a Microsoft open source project that provides an Objective-C development environment for Visual Studio/Windows. In addition, WinObjC provides support for iOS API compatibility. While the final release will happen later this fall (allowing the bridge to take advantage of new tooling capabilities that will ship with the upcoming Visual Studio 2015 Update),
The bridge is available to the open-source community now in its current state. Between now and the fall. The iOS bridge as an open-source project under the MIT license. Given the ambition of the project, making it easy for iOS developers to build and run apps on Windows.
Salmaan Ahmed has an in-depth post on the Windows Bridge for iOS http://blogs.windows.com/buildingapps/2015/08/06/windows-bridge-for-ios-lets-open-this-up/ discussing the compiler, runtime, IDE integration, and what the bridge is and isn’t. Best of all, the source code for the iOS bridge is live on GitHub right now.
The iOS bridge supports both Windows 8.1 and Windows 10 apps built for x86 and x64 processor architectures, and soon we will add compiler optimizations and support for ARM, which adds mobile support.