[simongr3dal]

The WWDC2019 video literally starts with the text:

"All Rights Reserved. This Broadcast and its contents are the sole property of Apple and are protected by Federal Law and International treaties. You are strictly prohibited from making a copy or modification of, or from rebroadcasting, or re-encoding, this broadcast without the prior written permission from Apple Public Relations, excepts as may be permitted by law."

The whole video is published on YouTube, they could have just linked to the timestamp of the official video on there or on Apples own website.

[Zekio]

Pretty sure copyright law allows doing exactly what they are saying you are not allowed to do, through fair use

[reaperducer]

That's the "excepts as may be permitted by law" part.