I see things like the following on a certain coding challenge site:
Copyright 2009–2018 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
I also see 63 posts on CR.SE as of the writing of this question.
I'm not a fan of the overreach and attempts to exert otherwise unenforceable restrictions, but I'm no site owner either.
How does CR.SE handle these things? (... because I have a question about a challenge already mentioned in a CR post)