What is the key feature of open-source software?

The key feature of open-source software is that the source code is accessible to the public. This means that anyone can view, modify, and distribute the code. This characteristic promotes collaboration and innovation, as developers and users can contribute to the software and improve it together. Open-source software fosters a community-driven approach, allowing projects to evolve more rapidly as enhancements can come from any user, not just the original creators.

In contrast, options indicating restrictions on the software, such as requiring a subscription or being available only for educational use, fundamentally contradict the principles of open-source. Additionally, the idea that open-source software is distributed only with restrictions does not align with the open access that defines this category of software. Therefore, the access to source code is what clearly distinguishes open-source software from proprietary software, making it the correct answer.