Do you need permission to download islamic videos from the Internet?

I watch Islamic videos on the Internet, I really enjoy them and I have learnt a lot from them. I am not sure if the people who uploaded these videos online got permission from the speakers. They are mostly Islam related dawah videos so I guess it's no harm of downloading them but I am not sure. I don't want to do anything haram so do you need permission to download Islamic videos from speakers themselves?