Thank for this comment, I really appreciate this detailed post!
For the rules, because the SBS rule always says if a cell needs to change his state, the next rule is ignored. In fact, the program was supposed to support pattern rule where you define for all cell with a state n a pattern. And if the neighborhood of this a cellmatch the pattern, his value is changed (or not). Then the algorithm process the next cell. If the pattern doesn't match, the programm try another rule. And that's while there is a plus button and an option for multiple rules. Unfortunately for technical (slow) and interface (bad ui) reasons, I had to remove this rules.
For the exception, that's because the program failed to load images which are in the jar. But I doesn't know why. This is mysterious. I will investigate this weekend.