I really saw that YAHOO! MAKTOOB forums are displayed(viewed) completely in Arabic language. Thus, although I don't know what forum software YAHOO! MAKTOOB forums are using, I am wondering whether the licensed XenForo Forum software can be displayed in Arabic or not. If I will need to download add-ons to achieve this, then they will be downloaded for free?
Also, I will still have the interface of XenForo in English after installing Arabic. As a result, I will have Xenforo forum software with two languages.(I.e. I will have my forum displayed in two languages, of which one category will be in English and another one will be in Arabic)
Here a screen shot of the YAHOO! MAKTOOB forums: