Mars Volta prog??!!

When somebody says prog rock or prog metal, I automatically think of the bands that borrow from 70's and 80's prog (moreso 80's) like Dream Theater and whatnot... where's the distinction between bands like that and the mars volta? These guys are definitely in their own, original world of music imo.

 

So perhaps we have two meanings of prog then. All of those bands that copy each other constantly and bands whose music is progressive.