Definite addition to any list of this kind: if it's not one of the standard licenses like RMP's or some similar site-wide EULA, make sure your license file has a distinctive name, especially if you have unusual restrictions or permissions involved. Similarly, readme files shouldn't just be called 'readme.txt' unless you want them overwritten by the next guy who makes an item. Important info can easily get lost that way.

-D
---
It's all fun and games until someone loses an eye texture.