Generally it’s just better to ask, even if you were legally / ethically / morally in the clear.

• if someone doesn’t want it, it’s going to turn them against peertube / fediverse platforms
• they might not understand what it is, and use their platform to share those feelings

Meanwhile if someone DOES want it, letting them know will give them the option to do it themselves. It makes less work for you, and they will feel invested. If they want it and they don’t want to upload it themselves, at the very least they’ll let their viewers know that peertube is an option.

As for the legal/moral side, I still feel like there’s a reason why you shouldn’t do this but I’m not aware of what that might be.