what is compiler.jar?

[Elmapul]

its not required to make the test example works, it was used during the production of the other js files?

[beenotung]

it is used to minify the js file cryptico.min.js

[Elmapul]

and where is the source code for it?

[beenotung]

@Elmapul this is the entry point for the command line tool: https://github.com/google/closure-compiler/blob/master/src/com/google/javascript/jscomp/CommandLineRunner.java