GUAM
GUAM is, as the name implies, a GUI frontend to allow easy administration of MySQL users. It is written in Java and uses the Swing toolkit. Since it is a pure Java application, it is completely cross-platform and should work on any platform that has a full Java implementation (and maybe even some of the cut-down implementations). GUAM is released under the GNU General Public License (GPL).
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License
GNU General Public License (GPL)