When you first start off on MPGH, you're considered a leecher. Most people who join MPGH only join for the hacks and to download them. The more posts you have, the more that little title changes.
To make source codes, you must have an advanced or at least an intermediate understanding of C++. The people who make the source codes do it all from scratch, trial and error, until they get everything right. They are able to do this because they understand C++.