Hmm. According to everything I have been able to find, Yume Nikki is classified as an adventure game. The RPG Maker software seems to be a tool capable of being utilized for game creation in multiple genres, but the tool isn't really the focus here, is it?

I have to admit that I have never come across a definition that narrow before. For this community, a JRPG is a Japanese Role-Playing Game. There are some examples in the interests section of the community profile that may help clarify for you.