You have your personal blog/site, don't plan to develop anything else, just need a WYSIWYG editor (Redactor is a professional tool. If you're just playing around and need some free stuff — choose TinyMCE, CKEditor, etc.)
I'm a professional freelance developer/design studio, I sell my work to multiple clients.
I make my own commercial CMS for sale.
I make commercial plugins for 3rd party CMS and applications.
I want my support requests to be answered within 1 business day.
I may need technical support from time to time.
I wish to be able to ask questions about the Redactor.
I may need help with integration and settings.
I want bugs to be fixed for me faster.
I'm a web service owner/developer, I have got only one web site.
I'm a developer and I've created a plugin for X framework. This plugin will be used by other developers to make their own products for their own clients.
I make software which will be used by other developers to build their own builds of CMS to sell it as their own products.
I'm a developer and I make an open-source product (CMS, service, etc).