Commercial use requires payment to patent holders, free use does not (whenever end user does not pay to watch). I dont know how ad supported streams are categorized, probably commercial. For personal use, I wouldnt worry about the license. Worry when you start a streaming server and start making revenue.

No, e.g. the package x264 from videolan.org is free software (FOSS) with GPL2+ licence.

Never cared. I’m one of those people that would indeed download a car.