The gist

Almost everything on this Web site is CC BY-NC-SA 4.0.

Basically, you can do whatever you want with my stuff. I encourage you to repost it, edit it, anything you like! As long as you:

Allow others to modify and redistribute your version, too.
Don't sell it, monetize it, or otherwise try to make money from it.
Credit me - it's as easy as saying "~keith made the original" and linking to this Web site.

Source code

However, any code I publish is licensed under the GNU AGPLv3 instead (unless I say otherwise).

Essentially, this means that if you publish a modified version of my software, or a program that uses my software, you have to publish your source code along with it, under the same license. You also have to disclose the source code if you run my software as an online service.