RobotBuilder is a Java program and as such should be able to run on any platform that is supported by Java. We have been running RobotBuilder on Mac OS X, Windows 7, and various versions of Linux successfully.
Option 1 - Starting RobotBuilder from Eclipse
Option 2 - Locating the RobotBuilder .jar file
RobotBuilder is shipped as a .jar file (Java archive) included with the Eclipse plugins. In most cases you can simply double-click on the file in a graphical file browser for your operating system and it will start. For both languages, RobotBuilder is located in the wpilib/tools directory. This directory is in your user home directory, usually something like /Users/<username>/wpilib.