LinuxCAD. If you get the source and follow the build howto instructions in the makefile, it could be free. You're going to need a distribution that will have the tools ready. Something like Fedora or SuSE.
I am looking for a free autocad clone. Used to be you could get IntelliCAD for free. Now you have to pay for it or get limited editions. I don't like limitations. Is there a good free AutoCAD clone?