If you’re on an Unlimited Plan, the answer is "no way."
It’s an interesting looking setup, though. As a Joomla front end, it looks to comply with DreamHost’s ToS. However, being that it’s a template, at first glance it doesn’t look like it actually performs the functions required of a reseller. Personally, I’d never try such a thing because I’d be held responsible for whatever goes on within my plan and don’t want to lose my plan here due to some stranger under my plan doing something stupid.