Bernstein
It's a direct manipulation parametric curve modeler.
This is a work-in-progress. With this tool you can create 3D spline curves. Curves can reference (build on top of) other curves via parametric references.
Bernstein depends on https://sourceforge.net/projects/yathe/
There are no files to download. If you are interested check out the source code. In order to compile you will also need to check out Yathe source code and compile/install that first.