BrisCAD is a real alternative to the AutoCAD , moreover it provides support for the .DWG file formats.
A few time ago, the creators of BrisCAD have made the public release for Bricscad V10 version for Linux Operating Systems.
The Bricscad Linux Version V10 also provides the support for Diesel APIs, DCL, LISP, and more than 500, 3rd party developers who build the applications for the Linux.
At present, Bricscad Version V10 works perfectly on Ubuntu 9.10+, OpenSuse 11.1+, and on Fedora 12+. As Bricscad V10 is not available for free, so one can download its free-trial version valid for 30 days.