zlib question

Are there any restrictions when using the zlib module? If I wanted to create my own image format, could I freely?

Thanks.

http://www.zlib.net/zlib_license.html
http://www.zlib.net/zlib_faq.html

Would I still have to include that license if I created an image format?

If you're distributing source that includes zlib or a modification of it then yes.