At the moment this is a blob. However, the code for this dll is open source. 
We will eventually integrate our forked version as submodule and hook it with auto-building.
You can find it here:

Original:
https://github.com/namazso/SecureUxTheme/tree/library

Modified (remove sig patching)
https://github.com/spiritreader/SecureUxTheme/tree/library