Companies that manage open-source software have a message for cloud computing providers like Amazon: pay up, share your code or stop using our technology for free.

The tension stems from the fact that cloud providers like Amazon Web Services are increasingly relying on open-source software—which is generally available to use free of charge, with the expectation that companies will contribute code to open-source projects—to add new features to their cloud offerings. In the latest example, The Information has learned AWS has been developing two new cloud services based on open-source software—a popular database called MongoDB and a tool for processing real-time streams of data called Apache Kafka.