Stumbled on
Dwarf Corp. It is open source code and proprietary data but that really doesn't matter. They only support building on Windows. There is a fork that had almost everything build on Linux but the project has diverged enough it would take some work to update it. The bigger problem is that they used XNA thinking Microsoft was promoting this library and it would catch on. Microsoft no longer supports it. They managed to get it running on VS 2017 Community edition. I tried VS 2019 Community edition and was unable to get it to work. So it is open source but you probably can't make use of the code.