From the photos I think you still have to set the antenna somewhere stable to use it, so it won't work at sea or maybe even at anchor. Don't get me wrong, it'd be cool just to be able to sail around and have low-latency high-bandwidth access in every port!
I have picked up the dish in hand and walked around my rural block of land whilst on a social Google Meet call with a co-worker at Gitpod. He was wondering the same. Will it work? Turns out the answer is yes. Was pretty wild walking around a paddock with iPhone in one hand and Starlink auto homing in the other. Didn’t really miss a beat until I tried spinning on the spot lol.
While they are officially recommending mounting the antenna rigidly, lots of people (including the grandparent post) report it working just fine when driving or otherwise moving dynamically. This isn't too surprising, since the phased array technology they're using allows instantaneous beam steering, and they need to support some amount of it anyway for high winds and wobbly mounts.
Their license only allows it to be used in fixed installations.
I suspect that the "while stationary" text is just lawyerspeak so they don't get accused of violating the license. If too many people post videos of using it while driving down the highway, they might have to add technical restrictions so they don't get fined for violating the license.