The Grunts 15mm sci-fi rules are now available for download.
From their announcement:
Grunts is now available for free download and is a dedicated 15mm fast play wargame designed for skirmish level play with between 10 to 40 figures per side using combined arms. You can use miniatures from any 15mm SCI-FI manufacturer. It is based around a generic platoon level battle, not restricted to a set genre or background setting. Vehicle and artillery rules are included for a combined arms gaming experience with statistics provided for all manufacturers of 15mm sci-fi and modern figures.