Definitely something created by Mr. House for just this occassion.

Knowing Mr. House and his love of Vegas, it's probably an AI created to attempt to simulate Mr. House and carry on with his plans.
This is also easier on the devs of course, cause it they say "the canon ending is an independant vegas" and then they give subtle clues in FO4 via rumors that the leader of Vegas "seems different lately" or something, then it opens up a whole array of speculation about whether or not it's Yes man or House (or even the Courier) in control without actually providing a definitive ending.