Xamarin has released an extension that allows licensed Unreal Engine developers to build games using C#. This initial release of Mono for Unreal Engine targets Unreal Engine 4.4 and supports development on Windows and Mac, with Linux support possible. The extension provides F# support too, with the Mono team intending to add default templates in a future release.
Native access to the external APIs for Android, iOS, and Mac is available now. C++ code can be accessed via CppSharp and manually binding C APIs can be performed with Platform Invoke. The team has provided a guide for getting started with this extension, and instructions are provided on how to configure a Windows or Mac based development environment.
In announcing the project, Xamarin’s Miguel de Icaza notes that currently Xamarin does not directly support the extension itself. To ship a project using Mono for Unreal Engine, a commercial license to redistribute the Mono runtime is required. (This is in addition to possessing a license for the Unreal Engine itself.) The development roadmap indicates preliminary support for Android and iOS, but has yet to make this work publicly available.