AGPL v3.0: Copyleft for Network Services

GNU Affero General Public License v3.0

The AGPL-3.0 is the strongest copyleft license in common use. It extends the GPL-3.0 by closing the "SaaS loophole" — requiring that users who interact with the software over a network (such as through a web application) also receive access to the source code.

The Network Clause

Section 13 of the AGPL-3.0 states: if you run a modified version of AGPL software on a server that users interact with over a network, you must make the complete source code available to those users. This closes the gap in GPL where a company could modify GPL software, run it as a web service, and never distribute binaries — thereby never triggering the copyleft obligation.

Key Characteristics

Attribute	Value
SPDX Identifier	AGPL-3.0-only
Type	Strong Copyleft (Network)
Patent Grant	Yes
Copyleft	Yes (strongest)

AGPL-3.0 vs GPL-3.0

The only difference is the network interaction clause. GPL-3.0 copyleft is triggered only when you distribute the software. AGPL-3.0 copyleft is triggered by distribution OR by providing the software as a network service. Everything else — patent grant, anti-Tivoization, compatibility provisions — is identical.

Business Model Implications

Many companies use AGPL-3.0 as part of a dual-licensing strategy: the open source version is AGPL (discouraging proprietary SaaS usage), while a commercial license is available for companies that do not want to comply with copyleft terms. MongoDB, Grafana (pre-license change), and various database companies have used this model.

Notable Projects

• MongoDB (before SSPL switch)
• Grafana (before Apache switch)
• Nextcloud
• Mastodon
• Various self-hosted SaaS alternatives