Ubuntu-AutoCAD Alternative: BRL-CAD
AutoCAD is one of the most expensive applications, but also indispensable for many types of jobs. Being so expensive, it’s a good reason to look for free alternatives. QCad is one of the alternatives but sometimes it’s just not enough.
BRL-CAD is a free, open-source alternative to AutoCAD, developed by the U.S. military in collaboration with NASA. It offers more than 400 tools, utilities, and applications comprising more than a million lines of source code. The package is intentionally designed to be extensively cross-platform and is actively developed on and maintained for many common operating system environments including for BSD, Linux, Solaris, Mac OS X, and Windows among others.