This is one of those cases where there are two hostas with the same name. Neither are currently registered with The American Hosta Society. The first one to be registered would become the "official" hosta of that name and the others would have to be renamed.

Originated by Viktoria Serafin of Glenbrook Farm in New York, this medium to large size hosta is a sport of H. montana 'Aureomarginata'. It is a green hosta with a narrow yellow to chartreuse marginal variegation. Very pale lavender flowers bloom in late July. The flowers are subtended by whitish bracts.

MyHostas database says that "It is smaller than montana 'Aureomarginata'. But early like its parent, watch frost!" This refers to the fact that H. montana 'Aureomarginata' is noted for emerging from the ground earlier than many hostas. It is therefore sometimes damaged by late spring frosts and might need to be covered to prevent damage on those nights.

Hosta Helper will call this plant 'Montana Moonshine' (Serafin)

Originated by Jim Anderson of Winterberry Farms in Georgia, this non-registered cultivar is of unidentified parentage.  It is a very upright large to giant size hosta with bright yellow foliage that has an irregular blue-green medial (center) variegation. The leaves are slightly wavy and come to a long point which bends downward. 

Hosta Helper will call this plant 'Montana Moonshine' (Jim Anderson)