I just dealt with another case with SE license confusion (look at the bottom, it says the contribution is public domain, even though it is not.)
This kind of confusion can be often caused by the small size of the legal footer:
site design / logo © {CurrentYear} Stack Exchange Inc; user contributions licensed under cc by-sa 3.0 with attribution required
If you cannot see it, here is a bigger version (more similar to the real footer):
site design / logo © {CurrentYear} Stack Exchange Inc; user contributions licensed under cc by-sa 3.0 with attribution required
And an even bigger one (+1 if you were unable to see the other two):
site design / logo © {CurrentYear} Stack Exchange Inc; user contributions licensed under cc by-sa 3.0 with attribution required
(okay, stop here)
Because this can be a real problem, especially for those with visual problems, I request for the footer to be enlarged. For some sites, low contrast is also a problem.