EOS ICO launched on Ethereum. EOS will not operate on Ethereum, EOS will have its own blockchain.

What they will do is take the EOS ICO tokens for those public keys that correctly registered on the Ethereum blockchain, and convert those registered public keys into the Genesis block for the EOS blockchain.

At which point all Ethereum EOS tokens are useless.

Also, this is USA legal lingo to cover your butt. "If and when someone launches a blockchain using EOS.IO software." They are disclaiming liability in case the project fails, this prevents lawsuits.

If I guarantee users to provide a product and never provide it they can sue. If I guarantee them nothing at all, then it doesn't give them much grounds to sue on. Most everything in the US works on that ideology.