Is it legal for people to create online text based games that.........?

Is it legal for people to create online text based games that are based off of things like pokemon, harry potter, lord of the rings, and other things of the such with out the person who owns it (author, companie, etc), post it online and just let people play with someone elses idea? Like on the link bellow, some 8 year old built an online text based game about pokemon, but does not have permision from the people who own the rights to pokemon, is that legal?



http://tppcrpg.net/Is it legal for people to create online text based games that.........?
As far as i know that website is not legal

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