Just as a small note for others, this project won't work correctly if you Download as Zip vs. git cloning it. The project requires the log30 library (which is included in a git clone, but not with download as zip).
If you download as zip, you will get "module '30log.30log-global' not found".
Now for actual feedback:
I really like the object-oriented approach you took when defining UIBox and UIText, however...
There isn't much documentation set in place for the classes that are being defined, such as UIBox or UIText having little to no comments. Even though the code generally is readable at first glance, it may be difficult for others to come in and extend the library.
