My only guess is that emulators don't support 1MB because no official game had that much.
(largest program ROM in a single game was 512KB)

Not quite. That's the total size of the PRG ROM and the CHR ROM. Just Breed's PRG ROM is 512 KB.

so, is this a better translation that what's currently out there?

What I'm more interested in is where this came from. Who is this guy, and how did he come from out of nowhere with his own FFIII translation? And why did he never bring it to anyone's attention afterwards?

Oh man, I thought I would never see this! There's a long story behind this work, I didn't think i was ever gonna hear about it again.

AD stands for Andrew (something)... man it's been 10 years now, I can't remember his last name. I think it was Andrew Church but I know that doesn't start with D.

Anyhow, this translation was made by the two Andrews, this "A D" guy you've heard from here and Andrew Vestal. These were the guys who founded "The Unofficial Squaresoft Homepage", which of course went on to become RPGamer around 1999 or so.

Around the time RPGe's Final Fantasy V translation and my group's Final Fantasy II translation were being worked on, I got word that these guys were translating FFIII. These guys weren't part of the translation scene though (which pretty much included a few websites and a few forums). From what I had heard, they intentionally were distancing themselves form us because they felt we were barely one step up from the warez scene. As I recall, they did the translation because this "A D" guy wanted a job at Squaresoft and did it as an homage and sort of a showcase of his abilities. As I remember "A D" did the translation and Andrew Vestal did the hacking. Or the other way around. Man it's been so long!

When we approached them to see if they wanted to play nice and release their translation to the public, they thumbed their nose at us. They went on and on about how the thing had been single spaced and all that, but they never publicized more than one or two screenshots. Som2Freak and I were pretty pissed about this, especially since translating the last remaining FF was on everybody's mind and it seemed like such a waste of time to start a whole translation when this thing was already done and polished.

In the end, Alex Jackson and SoM2Freak ended up translating FFIII (in a pretty short amount of time, if I may add) and people forgot all about the Andrews' version. Most people wrote it off as vaporware, designed as a ruse to add drama the translation scene.

I don't think I still have any of the original screenshots of their translation. The two that come to mind were single spaced and very text-heavy. And I do recall hearing talk about how they had expanded the ROM. Still, it's entirely possible this "A D" guy could be entirely somebody else that I don't know about. But, the fact that only outdated emulators can play this thing makes me want to think this is what I think it is.

I wonder if he got the job 

I applied for a translation position in a big company which I will not name, and they DID get back to me, but I haven't heard from them again. To be honest, I'm afraid they'll find out I hacked nintendo games and they'll try to sue me or something.

I can see why he'd be scared.

It's not that much trouble for the actual translators - the translation of the text itself isn't that bad, but it's the hacking parts that can get people in trouble...