This mod is a GUI library to ease the process of creating GUIs. Backported from 1.12.2 ModularUI. Requires GTNHMixins to work. This mod is under LGPL-3 license.
If you use Eclipse you can open the workspace found in \mcp9xx\eclipse. You will have to correct the library path for the vanilla jar and realms jar, and also add libraries for JRift, json, asm, and ...