Mono (software) | license

License

Mono is dual licensed by Xamarin, similar to other products such as Qt and the Mozilla Application Suite. Mono's C# compiler and tools are released under the GNU General Public License (GPLv2 only) (starting with version 2.0 of Mono, the Mono C# compiler source code will also be available under the MIT X11 License),[98] the runtime libraries under the GNU Lesser General Public License (LGPLv2 only) and the class libraries under the MIT License. These are all free software and open-source licenses and hence Mono is free and open-source software.

The license of the C# compiler was changed from the GPL to the MIT X11 license[99] to allow the compiler code to be reused in a few instances where the GPL would have prevented such:

  • Mono's Compiler as a Service
    • The Mono interactive Shell
    • The Mono embeddable C# compiler
  • Mono's implementation of the C# 4.0 dynamic binder.
  • MonoDevelop's built-in parser and AST graph

On March 18, 2016, Microsoft's acquisition of Xamarin was officially closed.[100] On March 31, 2016, Microsoft announced at Microsoft Build that they'll completely re-license Mono under the MIT License even in scenarios where previously a commercial license was necessary,[101] and Microsoft stated that they won't assert any "applicable patents" against parties that are "using, selling, offering for sale, importing, or distributing Mono."[102][103] It was also announced that Xamarin had contributed the Mono Project to the .NET Foundation.[102]