Pretty sure you want to use the AGPL and not GPL.
The ideal IMO will be some kind of experiment (probably something you should opt in). give people feeds and have them be ranked on a 1-10 scale and see which is better and do a Statistical hypothesis test to make sure the differences are not due to luck.






















I guess maybe set up a community on lemmy. have the client automatically make posts to it. or comments to a specific post?
Or maybe have a bot clients will send messages to?
Lemmy has a bunch of libraries for automation so that could be used to extract the information you need for the test.
Of course that probably makes it easier to feed fake data (e.g. if china wants to make lemmy.ml more popular).