All resources on AppendixSquared are free for personal and non-profit use.
Credit is not required, although greatly appreciated. (Sharing the website with a few designer friends would also be equally as appreciated, if you don't care to link back. Just saying.)
For commercial use, I would appreciate an e-mail requesting permission to use my work. I understand there's no way to regulate this, but I've put a lot of blood, sweat, and tears into this project. I will rarely deny the use of it, but would love to see what work you're doing.
AppendixSquared is completely run and owned by Christina Pham. All resources are free for anyone to use, but any donations would provide a great deal of help for keeping the website up. This is really just a suggestion for any die-hard fan with a few extra quarters and dimes sitting around. Feel free to e-mail me about any inquiries.