laian

Assuming you're familiar with a Unixlike command-like environment (e.g. Mac OS X's Terminal or Linux), this may be a useful guide:

http://gun.io/blog/how-to-github-fork-branch-and-pull-request/

Don't let the names fool you - JavaScript isn't Java; JavaScript is a far more modern and high-level language. ;)

Well, on the page I linked to, you can click around and read the JavaScript code. I'll try to find a good intro to Github while you do that.

As for your drafting idea: It's a good idea, but it would make it so you don't immediately jump into the battle, so it would probably be best as a separate ladder.

Of course you can help out with developing Pokemon Showdown!

It's open-source, so just go to: https://github.com/Zarel/Pokemon-Showdown

You might need to learn how to use Git and JavaScript, though. Feel free to ask me if you have any questions.