a parametric 3D CAD modeler
DXF2GCODE: converting 2D dxf drawings to CNC machine compatible G-Code
LibrePLM integrates CAD editors in Odoo / LibrERP
Python script for calculation of deflection of elastic ropes.
OpenNum lets you distribute solvers with a nice graphical interface
Open Knowledge on engineering development.
Simple CAD program
CNC control software