The SO content is licensed under cc by-sa 4.0, so theoretically someone could take it all and start again. Might work with enough of the resigning moderators behind it. But I don't think anyone could get enough of them behind it.
Why is it so important whether money transactions were involved?
I didn't understand what you were getting at with the comparison, they seemed totally unrelated to me. I think I see now though. If I look at it a certain way I see "receiving content and then relicensing it" in both circumstances.
I think that the context which needs to be ignored to make them the same in that way is very relevant though - the devil's in the details. In one circumstance you are posting content under the agreement mentioned above, in the other you are receiving content from someone who has agreed to no such conditions.
Seems like the disconnect here is whether SO should be able to put the relicensing terms in their terms of use and have that be enough. Personally I lean toward yes, but could probably be persuaded in the other direction. Would a check box next to the answer box be enough consent do you think? Or do you feel no one has a right to relicense any content they haven't produced themselves?
That may be, but they didn't put such terms in their terms of use. They just retroactively changed the license. Or rather, they fraudulently misrepresent the license of the content. It would be like Github relicensing all content they serve under cc-by-sa. It's absurd.
>Or do you feel no one has a right to relicense any content they haven't produced themselves?
You can agree to all sorts of terms. I didn't. A huge number of contributors didn't. SO would have to go back to all contributors and renegotiate terms with them individually. Of course, no such attempt has been made.
In my first comment I said cc-by-sa 4.0 because I had just gone to the site footer to see what license they were using. I knew it was some form of creative commons, but I didn't know which one.
I didn't know until just now that they are changing (or trying to change) the license on all existing content from cc-by-sa 3.0 to cc-by-sa 4.0. That I doubt they can do and I very much disagree with the move even if they can.
Interestingly, they also appear to have unilaterally changed the license on all content from cc-by-sa 2.5 to cc-by-sa 3.0 in 2011. The comment on Jeff Atwood's answer at https://meta.stackexchange.com/a/95033 is fun.