It’s more or less a consumer version of their RA2 system, which is its own protocol. The gateway interacts with the whole system using commands issued over telnet though, so you actually have a command line for operating and configuring it. It integrates with a bunch of closed systems, and it integrates right into Home Assistant with a first-party HA integration.
It’s not like you can inspect the source code for their firmware push up pull requests on GitHub, so I’m this aspect, yes, it is proprietary. However, with tools like Home Assistant, which is something you probably should be using, this becomes much less of a concern, in my opinion. It’s robust, high-quality, and is commonplace, so you can get bits and pieces at Home Depot.
If you’re interested in something that will work with mesh networks and you aren’t interested in running software like Home Assistant, you should look for Z-Wave or Zigbee hardware. Read reviews though; I’ve had a lot of mixed experiences with hardware, even from “trusted” vendors.
Whatever happens on my browser is client side, which is hardware and software I own. I can make what I own do what I want. It’s a right.
It’s like Google saying that I can’t skim a magazine in my home, and that I must read the ads. Google can do what they want server-side, and I’ll do what I want client-side.