I don't believe anyone has.
Nathan Dirks created it; it might be worth connecting with him to see if he would be willing to share thoughts on best practices for extending it.
https://driftlessdesign.com/What I know: The css is compiled-on-the-fly from SCSS/SASS to php, and it is based on the Foundation framework. Theoretically variables, etc. could be passed from a theme customizer to the scss compiler to allow site-by-site control over color, fonts, etc., but that was not part of the 1.0 version.