An Apache licence is a family of open-source software licences produced by the Apache Software Foundation, with the Apache License 2.0 being the principal version encountered in modern software projects. Apache License 2.0 is a permissive licence that allows users to use, reproduce, modify, distribute, sublicense and sell the software and derivative works, subject to specified conditions. It is designed to permit broad reuse, including incorporation into proprietary products, while providing more detailed legal provisions than very short permissive licences such as the MIT License. The licence is widely used for open-source libraries, frameworks and infrastructure software.
Apache License 2.0 includes an express copyright licence and an express patent licence. The patent provisions are an important distinction from many simpler permissive licences. Contributors grant specified patent rights covering claims necessarily infringed by their contributions or combinations with the relevant work as described by the licence. The licence also contains a patent-termination provision under which initiating certain patent litigation concerning the work can terminate the patent rights granted by the licence to the initiating party. These provisions are intended to provide greater clarity around patent risks in collaborative software development.
Apache License 2.0 allows commercial use and proprietary redistribution. A company can generally modify Apache-licensed software and incorporate it into a proprietary product without being required by the Apache License itself to release the entire product under Apache terms. However, when distributing the software or derivative works, the distributor must comply with the licence's notice and attribution-related requirements. This generally includes providing a copy of the licence, retaining appropriate copyright, patent, trademark and attribution notices as required, and marking modified files appropriately where the licence requires it. The precise obligations depend on the distribution and the contents of the original notices.
Apache License 2.0 differs from the GPL because it is permissive rather than copyleft. A project can generally combine Apache-licensed code with proprietary code without converting the entire resulting work to Apache-licensed software. GPLv3 includes compatibility with Apache License 2.0 in relevant circumstances, whereas GPLv2 has historically had compatibility limitations with Apache 2.0 because of differences in licence terms. This demonstrates that open-source licence compatibility depends on specific versions and conditions rather than broad categories such as "open source". Projects incorporating multiple licences should therefore analyse the actual versions and distribution structure.
The Apache licence also contains provisions concerning modifications and notices. When distributing modified versions, the licence requires appropriate indication that files have been modified. It also restricts the use of the Apache Software Foundation's trademarks and names except as permitted by the licence or otherwise authorised. This distinction between copyright permissions and trademark rights is important because an open-source licence does not normally give unrestricted permission to use an organisation's brand. A downstream project can often reuse the underlying code while needing to avoid suggesting that the original organisation endorses or sponsors the modified product.
Apache License 2.0 contains warranty and liability disclaimers. Like many open-source licences, it generally provides the software without warranties and limits liability according to its terms. Such provisions do not necessarily eliminate mandatory legal protections that cannot lawfully be waived in a particular jurisdiction. The licence therefore provides a defined copyright, patent and distribution framework but does not represent a complete contract covering every issue that may arise in a software business. Separate agreements may govern support, service levels, privacy, trademarks or commercial relationships.
The licence's structure is deliberately more detailed than the common MIT License. Both are permissive and commonly allow commercial and proprietary use, but Apache 2.0 explicitly addresses patents and includes more elaborate requirements concerning notices, modifications and redistribution. The additional text can provide clearer treatment of certain legal issues but also creates more compliance details to understand. Organisations commonly maintain attribution and licence records for third-party components so that required notices and licence copies can be supplied with distributed software.
The Apache License originated from the Apache Software Foundation's licensing practices and evolved into a widely used standard for collaborative software development. Apache License 2.0, released in 2004, is now a major permissive open-source licence. Its defining characteristics are broad reuse rights, permissive downstream licensing, explicit patent provisions, preservation of specified notices, a requirement to indicate modifications in relevant circumstances, and warranty and liability disclaimers. It is therefore neither equivalent to the MIT License nor a form of GPL copyleft, although all three are prominent open-source licensing choices with substantial use in modern software ecosystems.
