Matt Adareth developed and released his "Dactyl" ergonomic keyboard under CC license. This open source keyboard is described as “parameterized, split-hand, concave, columnar, ergonomic keyboard.”
As you can see it was 3d printed on a SLS machine but it could be probably made using other machines with some adjustments.
You can see a very interesting presentation by Matt about keyboard design and 3d printing at:
https://www.youtube.com/watch?v=uk3A41U0iO4 (video is not embedable). It is also great to watch if you are into more advanced OpenSCAD environment development.
All the files for it can be found here:
Here is a Reddit thread about it: