I looked at some recipes on this site but they were all Australian. I am trying to determine what makes it considered MUD as opposed to just plain ol chocolate?

Good question! I always assumed it meant very dark chocolate. But maybe someone can tell us the facts.

I've always known it to be very dark chocolate and dense or almost fudgy. I wouldn't consider a light and fluffy chocolate cake a mud cake.

What is a mud cake:

http://www.cakecentral.com/cake-decorating-ftopict-316303-.html

Pictures of mud cakes, Mississippi vs. AU mud cakes, other "mud" recipes:

http://www.cakecentral.com/cake-decorating-ftopict-529303-.html

Mud cake recipes, conversions, filling ideas and more:

http://www.cakecentral.com/cake-decorating-ftopict-358323-.html

HTH

Edited to repair broken links.