Difference between The Apache License 2.0 and the GNU General Public License (GPL)

The Apache License 2.0 and the GNU General Public License (GPL) v3 are two of the most popular open-source licenses, but they have different philosophies and requirements. Here's a detailed comparison of the two:

Apache License 2.0

1. Permissive Nature:

   • The Apache License 2.0 is a permissive license, meaning it allows users to do almost anything with the software, including using, modifying, and distributing it, with minimal restrictions.

2. Redistribution:

   • When redistributing the software, the Apache License requires that you include a copy of the license and a NOTICE file that includes attribution for any significant changes.

3. Patent Grant:

   • The Apache License 2.0 includes an explicit grant of patent rights from contributors to users. This is intended to prevent patent litigation related to the use of the software.

4. Compatibility:

   • The Apache License 2.0 is compatible with many other licenses, including the GPL v3. However, combining Apache-licensed code with GPL v2-only code can be problematic due to licensing incompatibilities.

5. No Copyleft:

   • There is no requirement to release derivative works under the same license, which allows integration into proprietary software.

6. No Warranty:

   • The software is provided "as is," without any warranties or conditions of any kind, either express or implied.

GPL v3

1. Copyleft Nature:

   • The GPL v3 is a strong copyleft license, meaning any derivative work of the GPL-licensed software must also be distributed under the GPL v3. This ensures that the software and any modifications remain free and open.

2. Redistribution:

   • When distributing the software, the GPL v3 requires that you include the source code or make it available under the same license terms. This ensures users have the freedom to modify and distribute the software.

3. Patent Grant:

   • The GPL v3 includes a patent grant clause that protects users from patent litigation, similar to the Apache License, but it goes further by prohibiting the distribution of GPL-covered software by anyone who engages in patent litigation against users of the software.

4. Compatibility:

   • The GPL v3 is explicitly compatible with the Apache License 2.0, but it is generally not compatible with permissive licenses unless the resulting work is licensed under the GPL v3.

5. Strong Copyleft:

   • Any software that incorporates GPL v3 code must also be released under the GPL v3. This ensures that all derivatives remain free and open source.

6. No Warranty:

   • The software is provided "as is," without any warranties or conditions of any kind, either express or implied.

Key Differences

1. Philosophical Approach:

   • Apache 2.0: Permissive and business-friendly, focusing on minimal restrictions.
   • GPL v3: Strong copyleft, emphasizing user freedoms and ensuring derivatives remain open.

2. License Compatibility:

   • Apache 2.0: Compatible with GPL v3 but not GPL v2-only.
   • GPL v3: Can incorporate Apache 2.0 code but requires the combined work to be licensed under GPL v3.

3. Patent Clauses:

   • Apache 2.0: Explicit patent grant from contributors.
   • GPL v3: Patent grant and additional protections against patent litigation.

4. Derivative Works:

   • Apache 2.0: Allows proprietary derivatives.
   • GPL v3: Requires derivatives to be open source and licensed under GPL v3.

Choosing Between Them

• Apache License 2.0: If you want to provide maximum freedom for users, including the ability to integrate the software into proprietary projects, and ensure some protection from patent litigation, Apache 2.0 is a suitable choice.

• GPL v3: If you want to ensure that all modifications and derivatives of your software remain free and open source, and provide strong protections against patent aggression, GPL v3 is the better choice.

Both licenses aim to foster open-source software development, but they do so in different ways, reflecting their underlying philosophies.