Heh, I thought that it was Object Pascal and Delphi.
Written in Java != Instant portability; looking at the icon in the top left, I assume this is written in C#. Therefore, I'd try running the editor again under Mono.
First: Mono have troubles with keyboard events or recognizing key codes sometimes.
Second: Why not Java != Instant portability; Java designed for crossplatform stuff IMO.
I think ImageJ a good idea, but don't forget about GTK+ and Qt, they were both crossplatform too.
BTW:
In addition, an archaic but still widely used way of storing map data is to simply define a series of data arrays/buffers in a game's binary; will you eventually support exporting tile data to C/Java/etc. arrays that can be inserted into a .h file and used in place of an external resource file? A feature like that would make such a tool much more useful for a wider developer's audience.
I think these arrays will make your code dirty or messy.