[odo1242]

They don't own the content according to the TOS, they get a license to use it (the Creative Commons Attribution-ShareAlike 4.0 license). They could still use it for AI training, but the model would have to be CC BY-SA 4.0 (not that AI companies care).

This definitely forbids the "I will not transfer it to others without permission from Stack Overflow" checkbox, as the CC BY-SA 4.0 license says "You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits."