... i'm not sure if this question has been resolved but just in case here is what i found, tested and already works perfectly on my Sprint's evo (rooted to froyo2.2 but no rom installed):
1. Download the Arabization libs from here:
froyo_evo_libs_arabic_android_plus_signed.zip
2. Drag to your Evo SD card
3. Power off your evo then Reboot to recovery
4. Once there, use "volume down" botton to select unzip file from SD card
5. Use "power" botton to select the downloaded file
6. Let your evo do the work, when finished reboot
7. Done!!
... a couple important notes:
1. You'll need to download an Arabic Keyboard.. i.e. Dr.Ben0x Keyboard..
from the Market (free)
2. You'll need to buy "Arabic Android" app ($6.99) from the market if you
want to get right-to-left alignment feature
Good Luck!