In order to use them for commercial projects, you must purchase the original pack that whichever icon you want to use came from, i.e. foods from Pack 3, weapons from Pack 4, etc.
Haha, no worries! Yeah this is a compilation of my existing icons made to fit MV/MZ's icon sheet, so RM users can get a feel for how they'd work in their games without needing to buy them first. :D
