I still have a hard time understanding where the AGPL copyleft feature kicks in on a product like Citus. Are you safe just deploying it as part of your backend?
Like, do you have to actually touch Citus's own code to trigger it? What if you start using some sprocs or sample connectivity code? Anybody know a good set of guidelines?
This is the entirety of the text which was added to the AGPL causing it to differ from the plain GPL:
> Notwithstanding any other provision of this License, if you modify the
Program, your modified version must prominently offer all users
interacting with it remotely through a computer network (if your version
supports such interaction) an opportunity to receive the Corresponding
Source of your version by providing access to the Corresponding Source
from a network server at no charge, through some standard or customary
means of facilitating copying of software. This Corresponding Source
shall include the Corresponding Source for any work covered by version 3
of the GNU General Public License that is incorporated pursuant to the
following paragraph.
In other words, if you deploy a modified version of Citus, your modified version is AGPL licensed, and thus you must provide the source code of this modified version to all users who interact with it remotely (e.g. through your web application).
What it does not state is that you must provide the source code of your entire web application just because you deployed a modified version of Citus, nor that your web application becomes an AGPL-licensed derived work of Citus because you used it over a network. The AGPL also does not require anything at all from you other than the plain GPL's basic requirements if the version of Citus you deploy is unmodified. (These are all incredibly common misconceptions on the internet, by people who've never read the license nor the GNU website.)
This is a different understand that I had on AGPL 3 quote FSF
"The AGPLv3 does not adjust or expand the definition of conveying. Instead, it includes an additional right that if the program is expressly designed to accept user requests and send responses over a network, the user is entitled to receive the source code of the version being used."
Have I misread this? As I understand AGPL3 is an extension of GPL 3. Therefore means if I use an AGPL3 licensed service I have rights to receive the code for this service.
The key word there is "the version being used". If you're using an unmodified version of Citus, the user is free to go get the source code from GitHub.
That's why the text of the clause itself makes a distinction about "if you modify the Program".
https://github.com/pg-sharding/spqr/blob/1.3.0/LICENSE (BSD2)
https://github.com/citusdata/citus/blob/v12.1.2/LICENSE (AGPLv3)