DualCAD!

LibreCAD (originally QCad then CADuntu) is an open source 2D CAD application for Windows, Apple and Linux. It is based on Qt, which is a leading cross-platform application and UI development framework.

Want to focus your time and energy on developing designs to build a better world? MicroStation easily models, drafts, maps, renders and documents your projects.

NttCAD: free, simple 2D/3D CAD software, multi-platform (works on Windows, Mac, linux...). Programmable in Java language. Small program size and fast download. Saves in autocad dxf, svg and NttCAD formats.

2-D engineering drawing editor that supports hierarchical object description. It is inspired by Hewlett-Packard's proprietary HP PIGLET (Personal Interactive Graphic Layout EdiTor), which later became the commercial Graffy editor by DURST CAD.