Passion is good, but it should never be used to overwork or underpay people. Never shit on someone else for having a good work/life balance and accuse them of not being passionate or whatever. That's a toxic work culture and honestly, given how much money is going around in software development, it shouldn't be necessary.

Pay people if you need them to work overtime. In hard cash, not vague promises. And if you've burned through your VC money already, don't try and push through on debts; cut your losses, give your employees plenty of heads-up, and pay them before your money runs out.

I mean if you don't want to hire them part-time, someone else will.