Welcome to GameMaker Touhou Engine (GMTE)'s official site.
GMTE is a game engine made specifically for creating Touhou Project-like fangames. It contains many premade scripts and objects to make developing games as simple as possible.
It is fully open-source, meaning anyone is free to make modifications to it and redistribute those modified versions. Currently it is in beta stage, but it is being updated semi-regularily.
On this site, you'll be able to find the documentation, changelogs and latest builds for download.