Open Combat is currently available in PDF format from the Second Thunder website, and has been very well received. We're now trying to move to the next stage of development, and produce a printed edition.
Second Thunder is now running a Kickstarter campaign to attempt to get the rules into print. Your can find the Kickstarter campaign here.
The current issue of Wargames Illustrated features a Rules Showcase about Open Combat this month (issue 329). You can read additional, supporting information related to the article on the Second Thunder website here.
In Open Combat, you can use any miniatures that you wish, and assign the profiles, skills and abilities that you feel they should have on the tabletop.