I downloaded a shotty manual for my Gaplus. Didn't seem to have a switch setting for Free Play. I recently saw an add on CL for a Gaplus set to free mode. Did I miss the dip switch? or this an addon board ala Mario Bros?
I haven't seen any Galaga 3/Gaplus freeplay ROM's, although that doesn't mean someone hasn't done one. I know it doesn't have a free play setting, but it does have a service credit button inside the coin door. Perhaps it's mounted on the outside, like mine is (courtesy of a previous owner)