Content is either CC-BY-SA, CC-BY-NC-SA, PD, GPL, or something else. Depends what it is.
If it looks stolen, assume fair use. Most things are CC or CC-NC depending on what's in them/where they came from. Original work is generally CC-BY-NC-SA unless it was originally somewhere else. If it matters, ask. This is a dumping ground, see. Copyrights generally aren't the first thing on one's mind when scribbling down random bits of ideas.