Links to DBA & HOTT Adaptations...
De Bellis Jacobitis (Jacobite Uprising Variant, 1745 AD) by David Medlock.
DBA-esque Fast Play Napoleonic Rules MkII by David Manley. [broken link}
DBA 4 AWI by Dan Abbott
AWI-DBA (American War of Independence), by Paul Potter
Napoleonic DBA by Steve Burt.
De Bellum Napoleonica by KISR
DBA-ACW, an extension for the American Civil War by Craig Cartmell. [Removed from the "Free Wargame Rules" Wiki]
De Bellis Americanus, a DBA extension for the American Civil War by Craig Cartmell (in PDF format).[Removed from the "Free Wargame Rules" Wiki]
The Vae Victis DBA-esque rules (128Kb PDF file), translated from French by John Gillson with permission of the publisher, cover the Napoleonic (La Grande Armee), Mexican-American (Los Gringos), American Civil (Rebel Yell) and Franco-Prussian (Kepis Rouge) wars.
DBA 1500-1900 Extension (aka Humberside Extensions or DBA-HX), by the Humberside Wargames Society. See also DBA-HX group and Alexei Gartinski's Universal Elements for use with the DBA 1500-1900 extension.