This stuff uses SLF4J, but no SLF4J implementation was provided. The result is having lines like this printed:

    SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
    SLF4J: Defaulting to no-operation (NOP) logger implementation
    SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

I suggest bundling an SLF4J implementation, and perhaps bundling a configuration defaulting to stdout output, while still accepting a configuration file for logging. I've done so with AVSL, bundling a configuration file whose name can be overridden with an environment variable, though we should probably go in the direction of Logback.