UML on limbo

I remember reading (somewhere) when limbo first came out they were 
incorporating
some type of virtual kernel feature, is that User-Mode-Linux?

I am asking cause I just found out about UML yesterday and have been 
reading on it non stop ever since, it sounds like one of the linux 
worlds greatest projects! I hope to see this dumbed down into a few 
RPM's by the RedHat team in the future (that includes Monday :)