no problem to use just script inclusion. But you should include not external js included into application but onw which bundled with RichFaces in order to avoid conflicts.
check loadStyle richfaces-demo sample in order to learn how to include stylesheets from jar's. And wiki faq contains entry on that.
Thanks for the tip. Solved it with this:
<a4j:loadScript src="resource:///org/richfaces/renderkit/html/scripts/jquery/jquery.js" />