Something that would be extremely helpful with the partial source is some type of documentation on the API or at the very least comments in the code.  I am guilty of not commenting my code as well, but if I am planning on others, especially customers who purchased the source code, reading my code then I would certainly do so.  It seems that whenever someone brings up this point, the answer is that this forum is the documentation, but I really don't think that a handful of posts and responses satisfies the requirement for documentation.  The extensions to the module we were planning are going to take much longer to implement because of the amount of time we must spend analyzing the source and trying to determine how things work.