Well, I can only give you my word and point you to the public GitHub repo here: https://github.com/SpaghettiLord1010/TModMaker/releases

Do note that the application is outdated and is not "complete" for the newest version of Terraria.

The tool isn't more then a simple program that creates a slightly more fleshed out skeletton, it can do a few things and those decently but if you want to make any major changes, this isn't for you.