Is the AGPL not a copyleft license? What are the derivative works you're required to distribute as AGPL?

AGPL is meant to address the situation where someone takes GPL code, such as a database server, runs it on their systems (possibly with proprietary modifications), and provides network access to it to users, and does not provide those users with the source code. That is perfectly acceptable under GPL, GPL doesn't trigger if you aren't distributing the program.

What AGPL changed is that they made it trigger on distribution (like GPL) and on interactive access of modified versions over a network.

If Amazon's plan had been to make money by hosting a proprietary fork of the server, which would give them some sort of advantage over other clouds like Azure or Google that only have the non-proprietary version, AGPL would thwart them.

But that doesn't seem to be the case. They don't appear to trying to make it proprietary. They seem happy to run the same code that everyone else does. They are making money from it by selling management and support services for it.

AGPL doesn't impede doing that at all.

If you're using a database that's not tightly integrated into your project and distributed with it, I don't believe you'd have to open your project. The API is the boundary:

- your project running on Linux kernel doesn't become GPL

- your project talking to MySQL doesn't become GPL and one talking to mongodb pre-2018 doesn't become AGPL

- your project talking to elasticsearch wouldn't become AGPL

(However AWS search offering... could?)

If you modified the software and then sold a hosted solution using the modified software you would need to release the source code for your modifications. Or if you built a plugin that was directly linked to the software you might have to release the source for that plugin. But if you had other software that made network calls to the software I'm pretty sure you wouldn't have to open source that as well.