It's a map editor called Final Fantasy 3 Map Editor (duh!), made by sleepydude. It's a recent one, released on june 2007 I think.
With that, you can modify every 400+ maps from the game and you can also modify the tilesets. There's also an NPC, Treasure, Event and Entrance editor.
There's a bunch of cool features! you can find it here: http://www.zophar.net/wwwthreads/attach ... ost=296519
EDIT: I'm adding FFVI Advance enemies and bestiary scene to the SDK
With that, you can modify every 400+ maps from the game and you can also modify the tilesets. There's also an NPC, Treasure, Event and Entrance editor.
There's a bunch of cool features! you can find it here: http://www.zophar.net/wwwthreads/attach ... ost=296519
EDIT: I'm adding FFVI Advance enemies and bestiary scene to the SDK