GPL v3.0: Strong Copyleft for Software Freedom
Understand the GNU General Public License v3.0 (GPL-3.0), the strongest copyleft license. Learn how it ensures software freedom and what obligations it imposes.
Detailed Explanation
GNU General Public License v3.0
The GPL-3.0 is the latest version of the GNU General Public License, published by the Free Software Foundation (FSF). It is the gold standard of copyleft licenses and is used by projects like GCC, GIMP, WordPress (GPLv2+), and the Linux kernel (GPLv2).
What is Copyleft?
Copyleft means that anyone who distributes the software — or a derivative work — must make the source code available under the same license. This ensures the software and all its derivatives remain free and open source.
Key Characteristics
| Attribute | Value |
|---|---|
| SPDX Identifier | GPL-3.0-only |
| Type | Strong Copyleft |
| Patent Grant | Yes |
| Copyleft | Yes (strong) |
Permissions
- Commercial use — Commercial use is allowed
- Modification — You can modify the code
- Distribution — You can distribute copies
- Patent use — Includes an explicit patent grant
- Private use — Private modifications do not require disclosure
Conditions
- Disclose source — Source code must be made available
- License and copyright notice — Must include the license
- Same license — Derivative works must use GPL-3.0
- State changes — Changes must be documented
Limitations
- Liability — No liability for damages
- Warranty — No warranty provided
GPL-3.0 vs GPL-2.0
GPL-3.0 added several important provisions over GPL-2.0: explicit patent grants, protection against "Tivoization" (hardware restrictions that prevent running modified software), compatibility with more licenses, and stronger anti-DRM provisions. The Linux kernel notably remains under GPL-2.0 only.
Use Case
Projects where ensuring all derivative works remain open source is a core value, such as developer tools, compilers, or applications where software freedom is paramount.