Denny's DVD (and other similar assignments) are deliberately written so that they cannot be used without the tweaks you mentioned. Putting the tweaks in shows that you understood the code, and have made it your own.
There is also a limit on how much truly original code & design can be used when Sun have strict guidelines as to what must appear in the user interface. Using design patterns is a good thing, and makes it easier for your code to be maintained. But then how many ways can the MVC pattern be applied .