What is the main feature of open source software?

Open source software is defined by its main feature of allowing users to access and modify the source code. This openness encourages collaboration and innovation, as developers can freely adapt and improve the software according to their needs or the needs of the community. This means that anyone can inspect how the software works, contribute improvements, fix bugs, and enhance functionality.

Unlike proprietary software, which typically restricts access to the source code and often requires payment for usage and updates, open source software provides a different philosophy centered around transparency and shared knowledge. This openness fosters a community-driven approach that can accelerate development and increase software reliability due to the extensive scrutiny from multiple users and developers.

Other options describe features that are contrary to the essence of open source. For example, requiring a paid subscription contradicts the basic tenet of open source, while restricting distribution contradicts its foundational principle of sharing. Thus, the ability for users to access and modify the source code is integral to what makes software open source and distinguishes it from other types of software licenses.