From Quake Wiki
Urban Mercenary is one of the first multiplayer games where you earned actual money for fragging online. Offline training bots are provided.
The engine provides basic 8-bit texture support and a new particle system. There is no model interpolation. There is also more effects with the familiar glow cone effect. There is also a point-and-click mouse driven menu interface.
Lack of source
Although there are GNU GPL v2 notices provided with the game, the source code for the engine was never made available. The QC progs source however is available with the game.