Java.Inquisition is a desktop application for creating and taking computer-based tests and quizzes.
Cheating is fully supported, so it`s only going to be useful for things like mock exams and self-assessment rather than administering formal exams.
Java.Inquisition is free, open-source software (see License). It is written in (you guessed it) Java, and should therefore work on any platform where Java is supported (including Linux, Mac OS X and Windows).