Here's an image of the Muddy Drive (on the left) compared to the Joyo "Ultimate Drive" (on the right):
And if that's not enough here's an image of the top side of the Muddy Drive PCB:
Now, there's nothing technically/legally wrong with doing this. I just think it's a bit cheeky, wouldn't you agree?
Here's the topic on freestompboxes.org: http://freestompboxes.org/viewtopic.php?f=7&t=16287