Which of the following is a common characteristic of proprietary software?

Proprietary software is defined by its licensing arrangements, which typically restrict access to the source code and limit how users can interact with it. The licensing agreement often entails that users must purchase the software for use, and this purchase can come with specific terms and conditions outlining how the software can be used, distributed, or modified. This characteristic reflects the business model surrounding proprietary software, distinguishing it from open-source software, which is usually available for modification and redistribution.

The other characteristics listed do not align with proprietary software. For instance, proprietary software does not allow users to modify it freely, as access to the source code is restricted. Furthermore, it is not commonly shared and redistributed without limitations; rather, the license typically controls how the software can be shared. Lastly, while some proprietary software can be offered for free, it is not universally the case that all such software is free of charge; often, it requires payment. Therefore, the correct answer highlights the typical licensing structure that governs proprietary software.