Lets see it from the beginning, if you want to make a server you have to fix,edit,rework,adapt in order to make your server stable. Always you will use a base project to avoid writing from scratch (l2j), so the goal is to gather some people who want to setup a server to fix the existing bugs and write anything missing to create a stable base server.
After doing this, anyone can adapt anything on it, since it doesn't missing anything. You can remove components, add new, make custom, but you have a stable base where you can do anything you want..
As more people contribute the project grows faster and all members of the team would get their server faster online. Even if I want to make a high rate epic pvp super duper x9999999 with RB's on gm shop i need to fix some serious bugs on it, so i find these bugs report them or fix them. I mean, I dedicate to what I'm interested in, but not all members want this kind of server, one wants a low rate server fully functional(quests, GBs, AIs,) he focuses on this part, and projects goes on.