Apache License 2.0
The Apache License is a permissive free software license that provides strong patent grants, and a clear, concise statement of your obligations in the license. It includes an express license to patents from contributors, and allows software and derivative works to be distributed under other licenses.
License Text
Apache License
Version 2.0, January 2004
http://www.apache.org/licenses/
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
1. Definitions
"License" shall mean the terms and conditions for use, reproduction,
and distribution as defined by Sections 1 through 9 of this document.
"Licensor" shall mean the copyright owner or other entity that grants
the rights under this License.
"You" (or "Your") shall mean an individual or legal entity exercising
rights under this License. You accept the License and agree to be bound
by its terms and conditions
[The full license text would continue here with all 11 sections, but is abbreviated here for brevity]
Key Features
- Permissive with strong patent grants from contributors
- Requires preservation of license notices in distributions
- Allows distribution under other licenses
- Includes a notice about changes to source files
- Compatible with the GPL and many other licenses
When to Use This License
Choose the Apache License 2.0 when:
- You want to protect against patent litigation by requiring a patent license
- Your project includes code that might be covered by existing patents
- You want flexibility in derivative works while maintaining proper attribution
- Your project includes or might include corporate contributors
Patent Terms
One of the most significant features of the Apache License 2.0 is the express patent grant. This grant is reciprocal: if you sue anyone over alleged patent infringement relating to this software, your license is terminated. The grant allows contributors to make additional patent licenses to users of the software.
Notice Requirements
You must retain the original copyright notice and license in all copies or substantial portions of the code. You don't need to include the notice in every source file, but it must be included in the distribution.
License Summary
The Apache License 2.0 is particularly appropriate for projects where contributors want to protect against potential patent litigation and ensure that users understand the rights they get when using the software. It's often preferred for Apache-licensed projects because of its clear rights and extensive patent protections.