This is an advanced topic, this is not required to use or develop for Opera Unite.
To run the Opera Unite service non-stop, you could probably rent a cheap VPS, install Linux with X environment on it and run Opera on that server (you can run virtual desktop with VNC →).
This is pretty feasible.
The only concern here is performance, but that's something I'd have to test soon.
This article is a stub, it contains information that doesn't explain subject fully.