Based on email exchange with dimcoin, the "no US residents" request is for fiat payment. Quote from an email to me "You can use ETH for sure because invest in a ICO doesn't fall under US law"
But then why would they say that US residents can only participate through an exchange after the ICO? They seem to go to great lengths to make it known that any and all US Citizens/residents/etc. are not allowed to partake in this ICO directly...
I had some questions, like you, so I went to their site and saw their email address. I sent an email and they responded rather quickly.