Very interesting proposition, I hope the company flourishes! I'm not HR but I'm pretty sure the anti-overtime provision is completely illegal at least in countries like the US and Canada. I would outlaw overtime instead of pay people less for overtime.
This is incorrect. The tldr is that US employees are either "exempt" or "non-exempt". Without getting into pedantic details, employees can be categorized as exempt if they make over about $23k/year. Exempt employees are not entitled to overtime at all, and the Fair Labor Standards Act doesn't prohibit reducing someone's hourly pay for overtime in the unusual way that Gumroad does.