Baby X is a Baby X windows toolkit. It's currently in a draft version.
The files have now been updated a bit to make them compile cleanly with the -Wall flag.
You'll also want the Baby X resource compiler . It packs images, fonts and string for use with Baby X or other software - you can use it outside of Baby X, and you can use Baby X without the resource compiler.
Version 0.2 uses embedded fonts rather than the X server font for drawing labels.
Version 0.3 implements cut and paste, unicode, and does all its own font rendering.