@drahardja bad news: any content you submit into Fediverse is basically broadcast into the datastores of any corporations that want to use it.
ActivityPub actually makes it harder to own data. It's very much a public broadcast medium.
@sj_zero on the other hand, since you're handing them content willingly, without a TOS specifying that you retain rights to the content, therefore they're free to use what you handed them.
TOS can restrict them. Without a TOS, they're free of that restriction.
Don't hand anyone content without restriction in the transaction if you want restrictions on the transaction.
@sj_zero copyright isn't a very solid basis on which to make a practical claim of ownership since not only is it extremely limited by different and complicated legal jurisdictions, but those limitations tend to be pretty significant anyway.
In other words, practically, copyright as ownership is a very weak claim.
That's why restrictions laid out in TOS are so important, if they're important to you.
And it's why ActivityPub/Fediverse if anything undermines those ownership claims.
All that being said, you are still absolutely correct. If I were to for example post the full PDF of the graysonian ethic, and people are going to download it and it is in fact if not in law me saying it's okay to take, and that thing that I downloaded for free I'm going to treat as if I can just hand it to whoever even though technically that's not really the case.
I seem to recall there were a few game companies that released copies of old games for free and said that those free copies of the games were not being released is freeware and they were still under copyright and yada yada yada, but come on -- if you downloaded a copy of GTA and GTA 2 off of the Rockstar website, you're not going to shed any tears giving a few copies to your buddies for some multiplayer.