The Pro version of JsIFR3 offers 5 possible styles in comparison to the free one, which only offers one style.
The one style for the free version is usually enough to fulfill the basic styling needs of most sites. 5 styles means that you can have 5 different fonts and sizes, each with as many CSS selectors as you want, But if you would like to either
a) support our ongoing effort to provide you with nifty extensions or
b) use more than one style in JsIFR3 or
c) use it commercially,
then the pro version is right for you. You are basically paying for the guarantee that we will help you fix any unforseen issues that may arise during the installation or configuration process of JsIFR3 Pro. Check out the documentation on the right for more detailed infos.