Ooh, the nasty bastards!
Tip #1 to a good business model: Do not rip off your customers!
To blatantly rip off your design and remove your branding is totally unacceptable, open source or not, to not ask if they could do so or even put a credit to you somewhere is totally unacceptable, especially for a company such as Altium.
(I must admit, I thought you worked for Altium with the level of detail and knowledge that you include in your most excellent videos!)
I would talk to them first, ask them to pull the video and remake it with your name retained, if they refuse, I don't know what you have in your country, here in the UK we have a "small claims court" which are supposed to be for things such as this, but you don't always win!