Safari 3 - Purchase or Automatic Update?

I haven't always used a Mac and haven't really been able to find the answer to my question. I noticed that a new Safari 3 will be released with the new OS X Leopard operating system. Will users have to purchase the new OS to get the new Safari 3 or does Apple release this as a free software update?

Thanks for the input!

Safari 3 uses a framework for WebClip that will most likely only be available with 10.5, so you'll most likely have to purchase the new OS, unless they figure out a way to get WebClip working within Tiger.