
So as I was looking over and analyzing the different rules sets, I discovered that there are actually quite a few free rule sets out there for Ancient Wargaming(AW).
Many fall into the "you get what you pay for" category, but I was pleasantly surprised that a few seem on par with commercial products available.
The only downside that I see to adopting a free rule set is the availability of supplements and expansions...specifically army lists. As I began to study the rules options, it became clear that a major part of AW is the composition of the armies, both from a game balance and historic accuracy stand-point. Unless the author of the free rules also provides free army lists, you are in for a lot of research and translating of information.
Anyway, here are some free rules sets to consider: (Several require that you contact the author by email or join discussion group)
Hoplon 3
Basic Impetus (free intro version of Impetus)
Ancient Empires
Arcane Warfare Project
Ancients D6
Fast'n'Furious skirmish
WRG Ancient Rules
Oh, and here's a site with more free rules than you could ever want:
Freewargamesrules