Microsoft was surprisingly open in this regard with C#. The C# language and the CLI bytecode are both ECMA standards (334 and 335) that could be implemented by

Microsoft was surprisingly open in this regard with C#. The C# language and the CLI bytecode are both ECMA standards (334 and 335) that could be implemented by anyone. Of course, this is with the realization that the .NET standard library gives Microsoft's C# implementation a lot of staying power.