What we know
The link listed for Unreal Tournament is pieter.com's Urban Terror page: "Play Urban Terror Multiplayer Online". Urban Terror is a free Quake III total conversion, so this is not Unreal Tournament. We have not found an Unreal Tournament browser port.
Links
Deep dive in progress
This page is a short entry. The full write-up (original game, who built the port, how to play, creators and sources) comes next.
We have not confirmed whether it needs your own game files. The engine is open source. Not legal advice. Never run a launcher or download from a page you do not trust.