select a smaller category to start with
I'm not sure how they approve editors in the WORLD section of the DMOZ, but generally speaking, your stand a better chance for approval if you start with a smaller category (less than 100 listings). Then show you can follow ODP editing guidelines. Once you have edited current category listings and added new sites to the category you may apply for additional (larger) category responsibilities.
Arab users no longer care about ODP because this section is really dead.
Do you speak for the entire Arab population or is this just your opinion?
Remember that this is a VOLUNTEER project. Editors will review and list sites when they have time and elect to do so. The only requirement to maintain editing privileges is to make one edit every three months. We do not exist to serve webmasters or site owners who suggest sites to the ODP. There is no one within the DMOZ who will ever put pressure on an editor to review and list sites.
If they do their work well, I won't even need to become an editor (which is not a privilege I believe, it is much work).
Currently there are several active editors in the World: Arabic section of the DMOZ. As volunteers we do not consider this work. We all do this for different reasons when we have the time, but generally the goal is to build a better Internet directory -- edited by humans. It's certainly your option as to whether to apply for editing privileges, or not - suit yourself.
In what language should I complete the form? Arabic or English?
I cannot answer that question. Maybe someone else can provide you with specific guidance.
Who will review my application? An Arabic or an English editor?
It is the META Editors who approve editor applications. I cannot tell you how many METAs in the DMOZ read Arabic.