There is a difference. Wikipedia and many open source projects cannot forcibly switch to paid model, because they are currently giving their content away under

There is a difference. Wikipedia and many open source projects cannot forcibly switch to paid model, because they are currently giving their content away under CC-BY or GPL and you can keep a copy of it. If they started charging, you can fork the project and continue charge-free. Google maps API is a service controlled by Google. You cannot replicate it and keep using it if Google changes its mind about the licensing.