...Codebases that are licensed under the GPLv2 may choose GPLv2, and so on. 6.x versions of the library require .NET 4.6.1 or a .NET Core version implementing .NET Standard 2.0. They also introduce potentially breaking public API changes covered in the changelog. 4.x and 5.x versions of the library require .NET 4.5.1 or later or .NET Core. For .NET Core users, 2.0 is the minimum supported version for 5.x series.