I've ported the (.fdf-map)-making part of the compressor to java, so hopefully just about everyone who can't use .NET 2.0 can now compress their DF map images to upload them to the map archive.
You can get the java version from the same place as the C# version: http://shadowlord13.googlepages.com/dfmap-index.html
All in all, if you can use the C# version, it's better - There's no reason to use the java version unless you can't use the C# version (which means anyone on a Mac, on linux, on anything non-windows, or on a really old windows like windows 98).
The java version uses Swing to show a simple GUI, which means you can't run it without being able to run graphical java stuff in general.
P.S. I used the 1.5 JDK (meaning for java 5), which means that if you have a Mac, or if you don't have Java 6 (1.6) yet, you should still be able to use it (as long as you have java 5, at least).
Limitations in the java version: Can only read image files and write fdf-map files, can't show a preview of the map, doesn't try to guess your DF folder, always requires you to specify the tile size, uses more RAM (despite using the same amount of data in the same size buffers as the C# version), may take a little longer to compress than the C# version, and currently doesn't remember where you last had it compress an image or what the last tile size you specified was (but I may attempt to implement those last two things).
There's more information on the page for the compressor.
[ June 05, 2007: Message edited by: Shadowlord ]
[ June 05, 2007: Message edited by: Shadowlord ]