As http://www.kpdus.com is no longer accessible, JAD Java Decompiler download is extremely hard to find. Here is a mirror where you can get JAD for various platforms.
Unzip jad.zip file into any appropriate directory on your hard drive. This will create two files:
For UNIX users: make 'jad' executable: chmod a+x jad
No further setup is required.
JAD is Copyright 1997-2001 Pavel Kouznetsov.
All rights reserved.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. THE SOFTWARE IS NOT DESIGNED OR INTENDED FOR USE
IN ON-LINE CONTROL OF AIRCRAFT, AIR TRAFFIC, AIRCRAFT NAVIGATION OR AIRCRAFT
COMMUNICATIONS; OR IN THE DESIGN, CONSTRUCTION, OPERATION OR MAINTENANCE OF
ANY NUCLEAR FACILITY. THE AUTHOR DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OFFITNESS
FOR SUCH USES. YOU MUST REPRESENT AND WARRANT THAT YOU WILL NOT
USE THE SOFTWARE FOR SUCH PURPOSES