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Javootoo.com
javootoo.com is the Look and Feel Source for both Java™ developers and end-users.

Developers will find new Look And Feel and Icons to include in their applications.

Users will be able to choose and change the Look And feel of their applications.

ProGuard [ GNU General Public License (GPL) ]
ProGuard is a free Java class file shrinker, optimizer, and obfuscator. It can detect and remove unused classes, fields, methods, and attributes. It can then optimize bytecode and remove unused instructions. Finally, it can rename the remaining classes, fields, and methods using short meaningless names. The resulting jars are smaller and harder to reverse-engineer.

JavaGuard [ GNU Library or Lesser General Public License (LGPL) ]
JavaGuard is a general purpose bytecode obfuscator, designed to fit effortlessly into your regular build and testing process, providing peace of mind that your valuable Java code is more secure against decompilation and other forms of reverse engineering

RetroGuard [ GNU Library or Lesser General Public License (LGPL) ]
The Java class file format exposes an enormous amount of information about your original Java source code. Using one of the many decompilers on the market, Java class files can be accurately converted back into source format. Your code is therefore open to review and reverse-engineering by competitors and to unauthorized modification and redistribution.