Here are the kickstarter guidelines:

http://www.kickstarter.com/help/guidelines

I don't think those read as though they rule out startups/for profit businesses, but they do rule out some of the destinations of the money (payroll, business expenses), so I'm guess you'd be limited to spending the money on the creative part.

In the case of diaspora for instance, they claim the money should go towards their 'living expenses while they work on the project', but that's pretty broad.

I'm curious what their motivation is to limit what the money can be spent on, after all that's hardly relevant as long as the project succeeds.