The "Gene Driver" is a bit of a colloquial term for those people who can use ARMs, such as Jude Maverick, and, to a lesser extent Yulie Ahtreide. They are highly prized individuals sought out by the various military organizations for their power. The "Gene Driver" term has been retroactively applied in some media (such as the Japanese web site) to apply to anyone who can use an ARM, even in those Wild Arms media (like Wild Arms 3) where using an ARM just isn't all that uncommon.