I am going to go ahead and add this tag to all of these in 3 days if nobody objects.
My reasoning is that first, all questions should have a winning criteria/question type. This search query that I put together that searches for questions without one of these tags reveals lots of restricted-source challenges.
Also, we need better organization if we want to get out of beta any time soon. If we do become a full-fledged SE site, much more content will start appearing, and we need to keep it clean and organized.
If anyone thinks the name could be improved, feel free to comment and suggest another tag name. Otherwise, since nobody has said anything else about this, I'll just add the tag so I get get on with my tag categorization project.
-- 3 days later edit --
I am now editing all the posts; therefore, I shall accept this answer.