WPF is not the best example of open source, as some components are still closed source. Though it only runs on Windows, a closed source operating system, so per

WPF is not the best example of open source, as some components are still closed source. Though it only runs on Windows, a closed source operating system, so perhaps that is not so important. https://github.com/dotnet/wpf/issues/2554 https://github.com/dotnet/wpf/issues/2554 That said, there are cross platform, open source .NET UI frameworks out there, including one that is inspired by WPF: https://avaloniaui.net/ https://avaloniaui.net/