Technically it'd be illegal if we used any of the original graphics/music, but then again, so are any sort of fanworks. The script itself is a bit iffier, since it's been translated. I don't think Square would really care though.
The real question is whether or not I'd ever get around to doing it.
EDIT: I wrote some code, and I think it'd be pretty easy to handle the game engine in Javascript. The real issues are:
1. Creating a game creation script/program (this would be tough)
2. Create a PHP script that outputs the scene/flag/handler information as Javascript
From there, it's relatively easy to load the objects/data and start running the game. Save/loading would be easy enough using forms and PHP.
Adding music support would take some time and research though.
Once finished, someone could then use the game creation tool to port Radical Dreamers, although it'd have to be done manually and it would take some time. A conversion tool might be possible, but I'd have to take a serious look at the format used for the game's translated script.
Before I seriously try anything like this though, I need to play Radical Dreamers through a few scenarios to determine what features are necessary. Unfortunately, the sour.exe patching program won't work in Mac OS X (for obvious reasons), so I'll have to wait.