I treat all my work as if it is under a CC BY-SA license, which means you can use it so long as you credit me and also use the same license. It's like a chain letter, every time someone wants to use stuff that's under the license, it creates another work under the license and it spreads.
There are also some less legal restrictions. None of these are really enforceable but know I will dislike you if you don't follow them:
Don't just straight up repost something I've done, put your own art into it. Keep in mind, even something on the level of a YTP is cool with me.
Credit me clearly, not just like hidden at the bottom of a youtube description in a block of text.
Contact me about it when it goes out (so I can see!).
