Affero General Public License - Compatibility With The GPL

Compatibility With The GPL

Both versions of the AGPL, like the corresponding versions of the GNU GPL on which they are based, are strong copyleft licenses. In the FSF's judgment, the additional requirement in section 2(d) of AGPLv1 made it incompatible with the otherwise nearly identical GPLv2. That is to say, one cannot distribute a single work formed by combining components covered by each license.

By contrast, GPLv3 and AGPLv3 each include clauses (in section 13 of each license) that together achieve a form of mutual compatibility for the two licenses. These clauses explicitly allow the "conveying" of a work formed by linking code licensed under the one license against code licensed under the other license, despite the licenses otherwise not allowing relicensing under the terms of each other. In this way, the copyleft of each license is relaxed to allow distribution of such combinations.

To establish an upgrade path from AGPLv1 to the FSF's AGPLv3, Affero, Inc. published the Affero General Public License version 2, which is merely a transitional license that allows recipients of software licensed under "AGPLv1 or any later version as published by Affero, Inc." to distribute the software, or derivative works, under AGPLv3.