Which type of software license allows users to modify the source code?

The choice of open-source licenses is correct because these licenses are specifically designed to allow users the freedom to modify the software's source code. Open-source software promotes collaboration and transparency by granting users the ability to access, alter, and share the code. This is a fundamental aspect of the open-source movement, encouraging innovation and improvement of software through community contributions.

On the other hand, proprietary licenses restrict access to the source code and generally do not allow modifications, as they are created to protect the intellectual property of the software developer. Subscription licenses and perpetual licenses both pertain to the terms and duration of software usage rights rather than granting rights to modify source code, and thus do not support code modification as a feature.