The contributors license their work with a creative commons license and more specifically "cc by-sa". This means that the if anybody, e.g. SE, wants to use the work of a contributor then they need to provide the (original) license with the works (or at least one that is not restricting the previous, but that is another issue).
Full site footer:
On the regular website this is done by making notice of this license with a link at the bottom of the page.
Mobile footer:
However, it seems to me that the version of the website for mobile phones does not include this link at the bottom, and any notice of the license is difficult to find (if any such notice exists).
This seems to be to save space on the small screens, but is it reasonable and correct?