Well engineering is basically building something and getting a finished product...reverse engineering is exactly the opposite...it's about having a finished product and then re-building it. Basically you just have to know how to program Battleforge from the ground up. From what I understand they have all the models, rigs, animations, textures, and sprites from the Battleforge Client...from what I understand it is now just about programming the AI and physics but for a game like Battleforge that can be a MASSIVE challenge. Honestly it's not something you are going to break into over night...I've been programming for YEARS and I could not reverse engineer a game like battleforge and if I was on the team I would probably just slow them down.
I can't speak for the developers but I would say if you REALLY want to help your best bet would be to start watching battleforge videos and pay attention to how the AI behaves and all the rules of battleforge and then when they release a playable version for testing go back and compare what they have done to the videos and see if you can spot anything that is off. Then when you do spot a bug or something that doesn't work quite right...let them know about it.
