OpenBRF is the cornerstone of the Mount&Blade modding. Made by Marco Tarini (mtarini) originally made with The Last Days of the Third Age module in mind (the Lord of the Ring based one). He was developing it inside of that community, but after some early revisions the tool was made public. It is meant to be used to preview and edit BRF files (Binary Resource Files), i.e. most content of the game (e.g. meshes and animations).