The Apache License is a permissive free software license published by the Apache Software Foundation (ASF). It grants recipients broad rights to use, modify, distribute and sublicense covered software while imposing a small set of conditions intended to preserve attribution and to manage patent rights. The most widely used form is the Apache License, Version 2.0, which clarified contributor and patent issues found in earlier drafts and is commonly chosen by both foundation projects and independent open-source developers.

Key characteristics

Unlike copyleft licenses that require downstream distributions to remain open source, the Apache License is non‑copyleft (permissive). Important features typically cited by developers and organizations include:

  • Broad rights: permission to use, reproduce, modify, distribute and sublicense the software, including in proprietary products.
  • Notice and attribution: redistributions must include a copy of the license and preserve existing copyright, patent, trademark and attribution notices. A separate NOTICE file can accompany distributions and its content should be preserved.
  • Patent license: contributors grant a license to any patents they hold that are necessarily infringed by their contributions; the license can terminate if a recipient initiates patent litigation.
  • State changes: when modified files are distributed, the modifier is expected to document those changes so recipients can trace what was altered.
  • Trademarks: the license does not grant rights to use the ASF or contributor trademarks beyond what is explicitly allowed.

History and development

The Apache License evolved from earlier, shorter licenses used by ASF projects into the clearer Version 2.0, released in 2004 to address contributor agreements and patent issues with more explicit language. The ASF uses the license for its own projects; for example, the long‑running web server project is distributed under it: Apache HTTP Server. Over time, many non‑ASF projects and companies have opted for the Apache License because it balances permissiveness with explicit patent protections.

Uses, examples and importance

The license is widely used for libraries, tools and large application codebases. Its permissive terms make it attractive for commercial use: software covered by the Apache License can generally be incorporated into proprietary products without the obligation to disclose source code, provided the license terms and notices are preserved. Major projects and ecosystems adopt it to simplify collaboration and corporate contributions. At one point, a substantial portion of publicly hosted projects used this license; for instance, an early snapshot of projects hosted on Google Code reported notable usage of the Apache License (Google Code data).

How it compares to other licenses

Compared with short permissive licenses such as the MIT or BSD licenses, the Apache License is longer and adds an explicit patent grant and termination clause plus requirements to preserve NOTICE contents. These additions make the Apache License more robust against certain patent risks while remaining permissive in redistribution terms. In compatibility terms, the Apache License, Version 2.0, is considered compatible with later versions of other licenses in many cases but is not compatible with some older licenses without special handling; organizations selecting a license should review compatibility with the licenses of dependencies.

For developers and organizations, the main practical considerations when choosing the Apache License are whether the explicit patent language is desirable and whether permissive distribution terms align with project goals. For more detail on the full legal text and common contributor expectations, search official ASF license resources or consult licensed guidance: the official license wording and project policies remain the primary authorities on interpretation and compliance (Apache License reference).