You typically join (or form) a group because you get along with them. I'm in five groups, some with some pretty great releases (not mine), and I'm a pretty shitty graphics coder.
In fact your phrasing "elite skills" made me chuckle a bit, it sounds like the kind of thing a 16 year old would say in 1994 :) (no offense intended)
I think most people don't release source code because a) it's just not really part of the culture, b) the code is shit and c) people want to make demos, not READMEs. I mean, in the end this is about art and expression as much as anything. Electronic musicians don't usually publish their music software source files either. There is not really any elitism behind this.
c) is also why write-ups like this one are so uncommon. (Cool stuff LLB!)
You need to prove on your own that you have the necessary elite skills to enter a group.