I am a newcomer at ECJ. I am currently using it for some multiobjective optimization, and for that purpose I wrote a simple Python code to calculate some common metrics used in MO problems with regards to the pareto front i.e. generational distance, spacing, spread, relative hypervolume. 
The code loads the fronts given by ECJ after multiple runs and compute the global pareto front for all the executions, plots it, and calculate the metrics.

The source is available at:

Please feel free to use it and change it to fit your needs. You are welcome to report bugs as well.

Hope is useful for someone :)

Best regards,