It depends on the context I guess. In the context of not software licensing, I would define it roughly like you said. Interfaces that are designed in a way tha

It depends on the context I guess. In the context of not software licensing, I would define it roughly like you said. Interfaces that are designed in a way that is not compatible with existing software or easily implemented by others. An example would be QT, the GUI framework for C++. It has it's own implementation of stuff that already exists in the standard library, like the string container for example (std::string). You can't use standard C++ types with QT and you can't use QT types with non-QT C++ libraries or types. I am not a C++ or QT expert so there may be some level of compatibility between the types when using generics or in general, but from my very tiny use of QT it seemed like you had to use their types.