Ok, just contacted a lawyer who knows the entire history and legal environment. You all know him, it's Romain.

The name UWH is not copyrighted, and can therefore be used by anyone.
The real problem is the rules, that are the intelectual property of CMAS.
Although created by the commission, it was in name of CMAS and therefore they are the owner. The fact that is was not a document made once, but modified over 9 times, proves even more that CMAS owns the rights.

If these rules, in any way, are used in Durban this could give CMAS a great posibility to strike. They can even forbid the competition of taking place. A similar action already occured in Switzerland during a Kind-ball game.
Changing the name of uwh doesn't change a thing to this situation, neither does reconstructing the rules. Even if 30% of the rules are the same, CMAS still has all cards in hands.

Unless the Durban organization finds a way to bypass this (hardly likely from a legal point of view) the only option they have is to make this a CMAS tournament and not calling it the World Championship, but for example the International Open tournament, or just World Cup as suggested earlier