Steve Burt has a set of free wargames rules for playing Napoleonics using DBA mechanics.
napoleonics
Resolve Napoleonic Rules
Resolve is a set of free wargames rules for Napoleonic warfare.
Simple Sails Rules
Simple Sails is a set of free wargames rules for Napoleonic fighting sail.
If We Could All Be Napoleon
If We Could All Be Napoleon is a set of free wargames rules for 15mm Napoleonics
Over The Hills And Far Away Napoleonic Skirmish Rules
Over The Hills and Far Away is a set of free wargames rules for skirmishes in the Napoleonic Era. The rules are designed with a cinematic bent, and intended for up to six players each controlling up to eight figures.