FCKEditor, Documentation, and Licenses.

I am developing a website for memberships. This application has a forum, blogs, and membership news pages that need an editor for data entry and modification. The website is a service: there is no distrubution of software. Final decisions have not been made as to how the website will pay for itself, though online advertisements are an option. That is, the service will not be absolutely free. It may be not-for-profit, but not really free. FCKEditor is a very likely candidate for my website. In fact, I have been succssful in integrating it into my system; though, the system is not yet live.

Some questions:

Do I have to purchase a license for FCKEditor? Or, just when the website is actually commercially viable?
Do I have to display the FCKEditor copywright notice at the bottom of my web pages? Just the pages that use the editor?
Can I link my users to the FCKEditor user documentation pages? Instead, can I modify the user documentation and link my users to the modified version?

Thanks,

Danny