Square Enix has published Japanese-language guidelines for derivative fan creations. These guidelines cover Nier Replicant, Nier Gestalt, Nier: Automata, Nier Re[in]carnation, and Nier Replicant ver.1.22474487139… In sort, all the Nier games!
Source: Kotaku – Yoko Taro Thinks Nier Violates Square Enix’s Own Guidelines For Fan Creations