Call Nashbar and ask - it's not clear from their product description, but my hunch says that even though they double as standard platforms *or* clipins, the clip is meant for road shoes.
If the pedals are meant for standard shoes, then yes, you won't ever be able to clip MTB shoes on them and will instead need MTB pedals (I started out with some great standard eggbeaters) or road shoes.
Good luck!