This is a minor change based on requests from users and staff.
I don't think we really communicate the Site license to new authors or offsite content creators very well, and I think there's a lack of understanding about what the license permits and requires. I don't think this is the complete solution for that, but I do think we could do more. I am aware there is a Licensing guide, this isn't intended to replace that, this is just intended to point people towards it if they want more information.
I've drafted up some changes to make to the 404 page and the Guide to Newcomers that I think would help with this, which are on the sandbox page linked here. I'm wanting to get people's thoughts on this, both the general idea (in favor of adding this to one, both, or neither of these pages?), as well as on the phrasing of it. I've leaned towards only highlighting the most relevant aspects of it, focusing on authors for the 404 page and potential authors plus offsite content creators
This is not intended to be a legal disclaimer or to fully explain the minutia of Creative Commons - that's what the links to the Licensing Guide and the CC BY-SA 3.0 license are for. It's just intended to make people aware of the most relevant parts of it, so that they don't post work without being aware of the license they're releasing it under.
I'll leave this discussion open for at least a week, then see where to go from there based on your suggestions.