The AGPL was created to deal with the so-called ASP (application service provider) loophole in the GPLv2.
When the GPLv2 was created in 1991, no one was concerned with the possibilities of SAAS (software as a service).
Software was distributed by floppy disks or tape, and no one ran applications over the Internet.
So, the GPLv2 didnt deal with this concept at all. The loophole was that some people took the GPLv2 to mean that they could use open-source software to provide software services without granting people the right to access the source code.
To cover this loophole, Affero, an online company that provides rating and reputation services for online volunteers, asked the FSF in 2000 to help it create a license that would let it distribute its code, while preventing other companies from taking the code, using it and hiding it within their corporate IT departments.
With the approval of the GPLv3, the AGPL was also incorporated, but that version was oriented toward papering over the ASP loophole.
This new version makes it explicit that developers can use GPLv3 and AGPLv3 code in common projects. By publishing this license, the FSF aims to foster user and development communities around network-oriented free software.