Hephaestus is a freeware computer role-playing game construction kit (often called an "RPG maker").  A map editor is included, and scripting is done in the Java programming language.  Hephaestus is written in Java, and therefore runs on every platform.

You've wanted to make your own computer role-playing game all your life.  Hephaestus 2 makes it easier than ever to make any adventure you can imagine.  Use your own art and sounds, or use the standard libraries.  Make "static" maps with the map editor, or create your maps entirely with code - even making mazes and dungeons that are different every time you play.  There's never been a better time to start writing your own CRPG!

New in version 2.00: A map editor is included, you can have multiple characters in the party, and scripting is now in Java.

Download Hephaestus: http://kuoi.asui.uidaho.edu/~kamikaze/Hephaestus/