Open-Source License Types

In the diverse world of open-source software, understanding the nuances of various licenses is crucial for developers and organizations alike. Licenses like Apache, Mozilla, GNU, and AGPL dictate how software can be used, modified, and shared, each with its unique set of rules and implications. This article delves into the distinctive features of these prominent licenses, shedding light on their specific terms and conditions to guide you in making informed decisions for your software projects.

Apache, Mozilla, GNU, and AGPL are different types of open-source licenses, each with its own set of terms and conditions that dictate how software can be used, modified, and distributed. Here’s a brief overview of each:

Apache License (most commonly Apache 2.0):
- Permissiveness: It’s a permissive open-source license, meaning it allows for significant freedom in using the software.
- Requirements: Users must include a copy of the license and any notices provided with the software in any redistributions. Modifications to the original software must be noted.
- Patent Rights: Grants a license to any patent rights held by the contributors.
- Compatibility: Compatible with the GNU General Public License (GPL) version 3.
Mozilla Public License (MPL):
- File-Level Copyleft: Unlike GPL’s project-level copyleft, MPL applies on a file-by-file basis. Only files containing MPL-covered code need to be open-sourced.
- Requirements: If you modify MPL-licensed code, those changes must be released under the MPL, but you can combine the MPL code with proprietary code.
- Compatibility: Not fully compatible with GPL, meaning software under MPL cannot necessarily be combined with software under GPL.
GNU General Public License (GPL):
- Strong Copyleft: Requires derivatives or modifications of GPL-licensed software to be released under the same GPL license.
- Requirements: If GPL-licensed software or its derivative is distributed, the source code must also be made available.
- Versions: GPL v2 and v3, with v3 having more explicit terms against tivoization (restricting software modification in hardware) and patent retaliation.
Affero General Public License (AGPL):
- Network Copyleft: Similar to the GPL, but with an additional provision that addresses the use of software over a network (like in web services).
- Requirements: If you run a modified program on a server and let other users communicate with it there, you must make the modified source available to those users.
- Purpose: Specifically designed for software as a service; if you modify AGPL-licensed code and run it on a server, you must provide source access to the users interacting with it over the network.

Each of these licenses has been created to address specific needs or concerns in the open-source community. Their differences mainly lie in how strict they are about modifications and redistribution (copyleft), and in how they handle patent rights and network use of the software. When choosing a license for a project, it’s essential to understand these nuances to ensure it aligns with your goals for software distribution and contribution.