GNU General Public License v3.0
Use freely, but if you distribute modifications, you must release your source code under GPL too.
Commercial use
✓ Yes
Modify
✓ Yes
Distribute
✓ Yes
Must open source changes
✓ Yes
Must attribute
✓ Yes
Patent grant
✓ Yes
What this license means
The GPL is the original copyleft license. You can use, modify, and distribute GPL software — even commercially. But if you distribute a modified version (or a program that links to GPL code), you must release your entire program's source code under the GPL. This is the 'viral' nature of the GPL — it ensures that derivative works remain free.
When you encounter this license
Fine for internal use (no distribution = no obligation). Fine for SaaS (serving over a network isn't 'distribution' under GPLv3). Problematic if you're building a proprietary product that ships to users — you'd need to open-source your code.
Watch out for
The key question: are you distributing? If your software stays on your servers (SaaS), GPL doesn't require you to share source. If you ship an app, SDK, or library that includes GPL code, you must share source. When in doubt, ask a lawyer.
Tools using GNU General Public License v3.0 (11)
Real-time performance and health monitoring
Radically simple IT automation
Static analysis for shell scripts
Network-wide ad/tracker blocking DNS
Open source alternative to Algolia and Elasticsearch
Leading open source web analytics platform
Personal music streaming service
Leading graph database
The Mullvad VPN client app for desktop and mobile
Self-hosted newsletter app
Multi Theft Auto is a game engine that turns Grand Theft Auto: San Andreas into networked multiplayer.
This guide is for informational purposes only and does not constitute legal advice. For licensing decisions in commercial products, consult a qualified attorney.