Ripple paper wallet: is "ripplepaperwallet.com" safe?
Considering the fact it has iframes (e.g ads) in it and they might have access to the parent (e.g http://ripplepaperwallet.com) DOM, I would say that even if it was an open source project (which I have not found any references to) I would say it relies on a third party that is not open source therefore theoretically can be not safe.    

As well, I did not see an offline version of it, which in my opinion is a good practice to verify integrity of paper wallets.