Wherever carpooling is legal - which is most provinces of Canada and the USA - you can use Poparide in combination with a rental vehicle.
In fact, it's a great combination and we see it quite often on the platform when people don't have their own vehicle and want to reduce their rental costs. When legally carpooling, your regular insurance applies and you are not tax-liable for the money collected through Poparide.
Since you'll have quite a few people in your car, we do recommend generous third-party insurance - but this is our advice regardless of whether you're driving your own car or a rental!
Please note that ultimately it is your responsibility to be aware of the specific laws in your locality.