Wow, someone is super butt-hurt, for relatively no reason.
The following is random speculation but then again so was this entire article so I think I am allowed.
As part of CliffyB's retirement package from Epic the my have been forced to sign a non-compete contract in which he would legally not be allowed to do any business that would compete with what Epic does for an amount of years setup in the contract. This kind of this is more common than you would think. Maybe CliffyB told everyone his plans as soon as he was legally allowed.
Maybe, Epic is the one that are the a-holes. Knowing the CliffyB's non-compete was going to expire maybe Epic announced the next Unreal Tournament 2 months before Cliffy was allowed to announce his next project to try and steal as much of his thunder as possible.
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Regardless I am pretty sure CliffyB can do whatever he wants in relation to starting a video game company and making a game.