The fop.jar in this fop.zip can be used to print arabic script.
To create this fop version I used the sources of FOP 0.92 beta. The files I've changed can be found in here: fop-a.zip. You also need a forms.txt and a shapings.txt file in your classpath (intl.zip). They are used by the intl.ArabicText class.
Remember: To print arabic script you need a font that supports ALL arabic characters including the inner ligatures.