You have to compile it with javac (jdk 1.8 seems to work perfectly). To compile it you have to download Jython as standalone jar file and use it as class path. Then you have to use the Main.java as main class (for MANIFEST.MF) and compress it to jar. Alternatively you can download the pre-compiled jar as release version.
Note: There must be a valid WordList.txt in the same directory as the .jar file! You can download an example in release section.