What browser are you using?
The video has a standard play button on desktop Firefox. In fact it is very clearly an embedded Vimeo video (branded and all).
Also your server assumption is very clearly stated right next to the video:
> Thanks to HTML5, once Guacamole is installed on a server, all you need to access your desktops is a web browser.
This is all in the top half of the landing page and even highlighted in green to stand out from the rest of the page.
I agree many FOSS projects have lousy landing pages but I've always though this one to be one of the better ones. In fact it is better than many commercial landing pages I've had the misfortune to, ahem, land on.