I have just published the source code for Finite element method at GitHub. You can find it at https://github.com/bhrnjica/bhmke.
The project is at very beginign stage, and contains very few samples and implementation.
Currently you can solve simple plane load problem, and calculate node displacement.
The more code will be added soon.
The project will be Cross OS and Cross Platform, and will be complatible with .NET Core.