What License Is Apache Released Under?

This article provides a quick overview of the licensing terms for the Apache Software Foundation’s projects, focusing specifically on the characteristics, permissions, and requirements of the Apache License. You will learn about what the license allows, its conditions, and how it compares to other open-source licenses.

Understanding the Apache License 2.0

The vast majority of software produced by the Apache Software Foundation (ASF), including the popular Apache HTTP Server, is released under the Apache License, Version 2.0 (ALv2). Adopted by the ASF in 2004, this license is a popular, permissive open-source software license that allows developers a high degree of freedom.

Key Permissions of the Apache License

The Apache License 2.0 is highly favored by both individual developers and large corporations because of its flexible terms. Under this license, you are legally permitted to:

• Commercial Use: You can use the software and any modifications you make for commercial purposes without paying royalties.
• Modification: You can alter, extend, or subset the original source code.
• Distribution: You can copy and distribute the original code or your modified versions to anyone.
• Sublicensing: You can grant permissions to others to use the software under different license terms, provided you follow the core compliance rules.

Core Conditions and Obligations

While the license is permissive, it is not entirely without rules. To remain compliant when distributing Apache-licensed software, you must adhere to the following conditions:

• Include the Original License: You must include a copy of the Apache License 2.0 in any distribution of the software.
• Retain Copyright Notices: You must preserve all original copyright, patent, trademark, and attribution notices from the source code.
• State Changes: If you modify any existing files in the software, you must add a prominent notice stating that you changed those files.
• The NOTICE File: If the original software includes a “NOTICE” text file, your distribution must include a readable copy of the attributions contained within that file.

Patent Rights and Protection

One of the most significant features of the Apache License 2.0 compared to other permissive licenses (like the MIT License) is its explicit grant of patent rights.

Every contributor to the software grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable patent license to make, use, sell, or import the software. Furthermore, the license contains a patent retaliation clause: if you sue anyone over patent infringement regarding the Apache-licensed software, your patent licenses for that software are immediately terminated.