About the actual translation quality, it's quite decent and faithful to the source. It uses the names from the French version though, and is based on the PAL V1.1 version (the one with the "political correctness", green blood, bug fixes...)
Typos and untranslated bits are very rare, which is quite the feat for a one man job. They, coupled with one single texture, are the reason why the progress is still at 99%. An updated patch is planned (to polish the font and fix the above mentioned issues), alongside one for Master Quest.
The technical aspect however...
The game is still displaying the text from left to right. But the text is justified manually by padding it with lots of spaces to make it look like it's right to left, hence why it's being based on the French version. For the same text, the French version takes almost twice the size of the English script, and the Arabic equivalent is usually shorter than the English one. Thus it's ideal for padding the text with spaces too make it look RTL.
For dialogues where timing is important, there is simply a line break. Not the perfect thing imho.
Most translators are fine with that (not that I would agree), since having to alter all English graphics including the font (a sine qua non condition for translating to that language) in addition to the actual text (though a tool, aka Arabic Script Converter, was created recently to alleviate that part) can get already pretty tedious at times.
It seems nobody in the painfully-small Arabic translation scene really bothered to learn assembly for the N64 R4300i, the PS1 r3000 (for the soon-to-be-released Final Fantasy VII project), or even the simpler GBA/DS/(3DS?) ARM... to do the required modifications to the code making the text appear RTL. And once the project has begun, it's too late to implement it without ditching all of the text-insertion progress made so far. The only RTL-hacked games were mainly for the NES, and some attempts for the SNES.
Two of the three released Captain Tsubasa Arabic patches have the distinction of being the only Arabic patches released so far (among the forty or so Arabic translations available right now) that were hacked to be RTL. (I'll never understand how those get more love than most other quality games and genres).
Well, the game itself was popular enough in Arabic countries alongside Super Mario 64 back then (even though you'd think the N64 would be overshadowed by the PlayStation, but it did pretty well there), even popular enough to appear in TV commercials as a way to advertise for some soda brand ("Miranda", I think).