What does 'open source' refer to in software development?

'Open source' refers to software that is made available for anyone to modify, use, and distribute. This model promotes collaboration and sharing within the community, allowing developers and users to contribute to the software's improvement. Open source software typically has a license that permits this level of access, making it a cornerstone of many collaborative and innovative projects in the tech industry.

The essence of open source lies in its ability to foster transparency and flexibility. By allowing anyone to examine the source code, it encourages a diverse range of developers to contribute, leading to a variety of enhancements, bug fixes, and new features. This contrasts with the other options, which imply restrictions either by limiting modifications to authorized users, implying ownership by corporations, or suggesting a proprietary model where access is under strict control.