What are some alternatives?
When comparing JustCAD and DraftSight, you can also consider the following products
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
SketchUp - 3D for Everyone
QCAD - QCAD is an application for computer aided drafting in 2D.
Draft it - Draft it is a CAD software package that allows to create, save, & print work with drawing tools that allows to create professional drawings for project.
FreeCAD - An open-source parametric 3D modeler
TigerCad - A completely free, simple technical drawing software (CAD)