How do open-source licenses differ from proprietary licenses?

Open-source licenses and proprietary licenses differ fundamentally in how they grant permissions and impose restrictions on software use, modification, and distribution. Open-source licenses allow users to access, modify, and redistribute the source code, often with conditions that preserve these freedoms for downstream users. Examples include the MIT License, GNU GPL, and Apache License. Proprietary licenses, by contrast, restrict access to the source code and typically limit how the software can be used, copied, or modified. These licenses, such as those for Microsoft Windows or Adobe Photoshop, prioritize the developer’s control over intellectual property and often require payment for legal use.

The key distinction lies in the rights granted to users. Open-source licenses fall into two broad categories: permissive (e.g., MIT, Apache) and copyleft (e.g., GPL). Permissive licenses allow developers to use, modify, and distribute code with minimal restrictions, even in proprietary projects, as long as the original license terms are acknowledged. Copyleft licenses require that any derivative work must also be open-source under the same terms, ensuring code remains freely available. Proprietary licenses, however, explicitly forbid modifying or redistributing the software without explicit permission. For example, a proprietary license might limit installation to a specific number of devices or prohibit reverse engineering, which are common in commercial software.

For developers, the choice between license types impacts collaboration, compliance, and project goals. Open-source licenses foster community-driven development, enabling transparency and shared innovation, as seen in projects like Linux (GPL) or React (MIT). However, they may require careful compliance with terms like attribution or copyleft obligations. Proprietary licenses offer tighter control and monetization opportunities but limit third-party contributions and transparency. Developers using proprietary software often rely on vendor support and warranties, whereas open-source projects depend on community or paid support. Choosing a license depends on whether the goal is to encourage widespread adoption (open-source) or maintain exclusive control (proprietary), balancing legal, technical, and business priorities.