Stuff on this site is under a variety of licenses, but there is a system for you to figure out which one applies.
Anything that's not my original work is under whatever license the original creator wanted - this should be indicated wherever I include someone else's stuff (but you get no guarantees).
Computer code snippets (under 25 lines) are under the WTFPL license.
Larger chunks of code (and complete programs, for the things I get round to finishing) are under GPLv2.
"Creative" stuff (photos, videos, prose... - anything copyrightable that isn't code) is under CC-BY-SA, except that I don't actually care about attribution so feel free to ignore that part (unfortunately CC-SA has been retired because too few people used it compared to CC-BY-SA).
All of the above licenses are merely the default, others may be specified locally to whatever thing I'm making an exception for.
If you're not sure which license applies to something, or you want to use something but the license doesn't work for you, get in touch. There's very little use that I'll say no to; but I might demand so much money that you'll say no.