I can use the module design PrimeFaces in a proyect
Yes you can include jar files, for example libraries.
You can see this thred in the forum with details
No, Prime faces is for .jsf technology, in WR works with Jsp.
No you can´t use primefaces. But with webratio technology you dont need this aspect is transparent to developer.
And use some kind of jar??
Yes, if you have a predefined .jar, you can to import in WR. For example, a .jar that manage json estructure.