LibrecadLibreCAD is a cross-platform 2D CAD program written in C++11 using the Qt framework. It can read DXF and DWG files and can write DXF, PDF and SVG files. The user interface is highly customizable, and has dozens of translations.
Openjscad.orgJSCAD is an open source set of modular, browser and command line tools for creating parametric 2D and 3D designs with JavaScript code. It provides a quick, precise and reproducible method for generating 3D models, and is especially useful for 3D printing applications.
mightyscape-1.XA maintained extension collection for Inkscape 1.0+, working on Windows and Linux
CadZinhoMinimalist computer aided design (CAD) software
PolyDraw✳️ PTSource PolyDraw is a free 3D polygonal modeller for Windows x86 and x64, for creating or modifying 3D objects using a mesh of 3D points and parametric NURBS Curves .Exports and imports to over 40 formats including WebVR and 3D Printing.
f3dFast and minimalist 3D viewer.
ACadSharpC# library to read/write cad files like dxf/dwg.
vectorexpress-apiVector Express is a free service and API for converting, analyzing and processing vector files.
xcsgXML based Constructive Solid Geometry based on carve
GERBER X3Program for preparing G-code for milling of printed circuit boards on CNC. You can use it as a converter to a PDF file.